There is actually much debate about the strength of Torch vs Pedro. While they both can be quite strong, they both vary by generally the same amounts. Some particular specimens can be very weak. The main reason why torch is said to be stronger is because of measuring by length, and not mass. Torches are generally quite a bit thicker and as such, would have much more mass per length.
There's really no way to tell, other than to take it. So just take it!
The worst thing that seems to happen with cacti is underdose, as even an overdose really doesn't seem too threatening. Cactus is very gentle and kind, and I really couldn't imagine having a bad trip.
If you can find some Bridgesii, also known as Achuma, that would be good, too. From what I've read, it seems to be more consistent and reliable than Torch or Pedro. They each have different personalities, though.
Be an adult only when necessary.