I would say 4-ACO-DMT seeing as how 4-ACO-DMT turns into Psilocin in the body, but also has it's own activity before metabolizing into Psilocin, plus 4-ACO-DMT is in pure powder form and can kick in moreso all at once, compared to eating mushrooms or perhaps drinking the tea, but mushrooms probably come in second.
There are likely other compounds which can get you close to what DMT has to offer, but each Psychedelic is going to be unique, and i would argue that it's chemical structure as well as it's binding profile is going to give it it's uniqueness, so DMT is DMT, Psilocin is Psilocin, etc, we may come close and even have similar or the same kinds of effects/experiences from different Psychedelics, but each Psychedelic will have it's own flavor and differences even with similarities.
Now, when it comes to Ayahuasca, Ayahuasca is not "just DMT", Ayahuasca is largely/dominantly the Harmalas, with the DMT being secondary, even if DMT is the sought after active, even if you use a lower dose of Harmalas, the Huasca imprint is there. Now, if you want oral DMT, your best bet is probably Moclobemide or some other MAO-A inhibitor which is rather transparent on the body, since Harmalas have other effects besides MAO-A inhibition.
Which brings me to my next point, Psilohuasca. Psilohuasca and Ayahuasca (ime using Rue for the Harmalas, Acacia/Mimosa for the DMT, mushrooms/4-ACO-DMT for the Psilocin) are pretty damn close ime, because the common/main factor is the Harmalas, making it a Harmala experience, with the DMT or Psilocin being the Illuminating/Psychedelic factor, they both bring me to pretty much the same territory, though again, with some differences but it's the closet i've come, the Huasca family
Now, ime, there's going to be differences depending not only on the main active (so DMT vs. Psilocin), but there's also going to be differences between DMT-containing plants and the plants vs the pure compound, or perhaps full spectrum extracts, and there's going to be a difference between 4-ACO-DMT and Psilocybin/Psilocin (and mushrooms as a whole) because 4-ACO-DMT is a pure compound, it is an active prodrug to Psilocin (active meaning it has it's own effects before metabolizing into Psilocin, whereas Psilocybin is supposedly an inactive prodrug meaning it doesn't exert it's own effects before metabolizing into Psilocin), and then you get into mushrooms which not only have other compounds besides Psilocybin/Psilocin, but i'm convinced even the fungal material gives things a "mushroomy" feel that contributes to the overall mushroom experience, which you may not get with pure Psilocybin, similar to how pure Harmalas or pure DMT do not have that planty feel that the plants have. With that said though, when i've had Psilohuasca, whether using mushrooms or 4-ACO-DMT, i've had this strange/odd occurrence of the Rue/Harmalas making the Psilocin feel way more mushroomy than mushrooms (the fungal "mushroomy" feeling aside) and i even keep getting like repetitive imagery of mushrooms, even using 4-ACO-DMT, which is crazy lol.
I've also experienced 4-ACO-DMT with Rue/Harmalas, taken at different times (so 4-ACO-DMT taken at the same time as the Harmalas, 30 minutes, 45 minutes, an hour, 2 hours apart), and on a few occasions i've experienced 4-ACO-DMT feeling like oral DMT, smoked DMT, mushrooms, and a combination of all three lol, just by playing around with the timing between the Harmalas and 4-ACO-DMT. And also the 4-ACO-DMT, if taken an hour after the Harmalas, unfolds in exactly the same way and with the same duration as mushrooms an hour after the Harmalas, due to the gut's MAO-A being fully inhibited by the time the 4-ACO-DMT or mushrooms are consumed, and with the 4-ACO-DMT you can feel it metabolize into Psilocin, the onset is a bit different than mushrooms because of the active effects but once it turns into Psilocin you can feel it and it feels exactly the same as mushrooms for the most part. Then, you also have the ability to take 4-ACO-DMT as a pure powder and kick in quickly, or make an edible with it and eat it (or dissolve it in some water and drink it) for a bit of a slower onset. And especially with it being a pure compound, you can take it on it's own, or in combination with Harmalas for Psilohuasca.
Overall, for me personally, the Huasca's are where it's at, whether using DMT, 4-ACO-DMT, mushrooms, or something else, the Harmalas are central to the main and overall medicine, the Psychedelic portion, while also being equally as important, is secondary, and an admixture. Therefore the space/territory is very similar, or perhaps even the same in some cases, even though the Psychedelic is different. And then on top of all that, you have the differences between the Harmala-containing plants (Rue, Caapi), and the pure compounds, which ime at least, i've found the Harmala source (whether plant, or extract) to be of most importance, whereas at least when it comes to DMT-containing plants and Psilocybin mushrooms vs 4-ACO-DMT, 4-ACO-DMT being a pure compound, i've found that 4-ACO-DMT works just fine as a pure molecule, just as good as mushrooms and DMT-containing plants, the biggest difference was whether i was using manske'd pure Harmine/Harmaline extract vs full spectrum Rue extract vs the Rue seed itself, preferring the seed itself, with full spectrum in second place, and didn't particularly care for the pure Harmine/Harmaline mix, with the seed itself having the overall better feel.
I'll say that because 4-ACO-DMT turns into Psilocin, but also can have it's own unique weirdness to it, and can be combined with Harmalas for a more DMT-like, Ayahuasca-like experience (the Harmalas making the 4-ACO-DMT, as well as mushrooms, more DMT-like), that's probably your best bet, if not 4-ACO-DMT, then mushrooms. But again, going back to the differences in binding profile between compounds, ime, Psilocin seems to so far lack the Adrenergic properties of DMT, and probably some other properties as well, which is actually quite cool (but also ends up missing out on some of the Adrenergic-related benefits), because that makes Psilocin smoother/gentler/more relaxed compared to DMT's intense and sharp seriousness, especially during onset, in which i find Psilocin to be overall less intense than DMT because DMT's main intensity comes from it's Adrenergic properties, which for me is a good thing because i mean i love oral DMT, but i don't particularly care for it's intense onset/come up, i much prefer the come up of Psilohuasca in comparison, they both still have the Serotonergic intensity though.
Another thing to keep in mind/take into consideration, is that oral DMT at least, seems unique in regards to it not building up a tolerance, i took it daily/near daily for 4 years straight at fully immersive dosages (in the form of Mimosa and Acacia) and it still worked just as fully all throughout, in fact things even become more manageable as i went along, partially because the Harmalas side-effect profile will clean up in the long run as it's reverse tolerance builds up (which is another cool thing, Harmala reverse tolerance, you take the same dosage, it just gets stronger and stronger, and eventually, cleaner/cleaer) but also because dosing oral DMT that regularly, the brain can adapt and shift and it gets accustomed to things which ime at least makes it easier to do more with it and be able to bring more back from it. And you just don't get that with mushrooms or 4-ACO-DMT, or even pure smoked DMT/Changa for that matter, although there are different ways one can go about it and if you really wanted to, heck you can even have a mix of it all, smoked DMT/Changa, oral Aya, or oral Aya+Psilo-huasca mix (which i've only done once and with a low dose, 800mgs iirc, of homegrown mushroom powder, with a full dose of Acacia, 4 grams of Lemon Balm, and my usual dose of Rue, and it was great!), there's differences between the plants, between the compounds, i mean you can really customize this shit to your liking if you really got in depth with it lol.
There's tons of different compounds out there, they may give you similar or even the same results as other compounds, including DMT, but each will be unique, and imo each compound has it's differences as well as similarities, but i do think each compound will be unique in what it has to offer, how it feels, how you experience things, it's effects, it's binding profile, and even the chemical structure itself lending a difference/imprint to the overall feel/experience. It's just about finding what resonates with you more, however, make no mistake, DMT is DMT, LSD is LSD, Ayahuasca is Ayahuasca, mushrooms are mushrooms, they are each unique and Ayahuasca especially is unique amongst all of the Psychedelics because the common element in Aya is the Harmalas, so the Huasca is a completely different universe compared to Psychedelic agents on their own, and i do not think you will get from LSD, for example, what you will get from Ayahuasca, or even from DMT in general, there may be some overlaps, but they are completely different kinds of experiences, especially since most people take low doses of LSD, or mushrooms, compared to the onslaught of full immersion that comes with a Huasca experience, whether Aya or Psilo-huasca.
But lastly i will say this, i believe DMT to be special, amongst all other Psychedelics, because it's an endogenous neurotransmitter/neuromodulator and is produced by the body. That's not to say other Psychedelics are somehow inferior, because they all hold great value and promise imo, but DMT is perhaps Nature's original Psychedelic, which even spawned Psilocybin and Psilocin (4-PO-HO-DMT/4-HO-DMT), as well as Bufotenin (5-HO-DMT), and 5-MEO-DMT, which, at least 5-MEO-DMT and Bufotenin, from my understanding, are also endogenously produced, as well as N-Methyltryptamine (NMT) and who knows what other endogenous Psychedelic compounds are produced, but overall, DMT seems to be King Psychedelic in Nature, and as such, nn-DMT in itself, is unique, original, and the root Psychedelic for other naturally-derived DMT-based compounds. Couple that with the fact that oral DMT seems to have no tolerance, and it is perhaps the best/top Psychedelic, on planet earth (so far) that one can use to fully, consistently, repeatedly/regularly, and for the long term - experiment with, explore, learn from, and study, there's just no real comparison imo between DMT and other Psychedelics precisely because it's the only Psychedelic we have that can give us regular, consistent, ongoing, and long term access to these states. Plus again, there's going to be differences between all Psychedelics in terms of their uniqueness, so DMT really truly is special, imo, compared to other Psychedelics, so there is indeed a case to be made for DMT's special status.
Also i will add that ime, most of what i experience comes from within myself, it's to do with the body, it's in everyone, the compound is the tool, the catalyst, the aid, to help induce these states, regardless of their individual differences/uniqueness, even though their differences/uniqueness can imprint upon/flavor the experience.