I was always under the impression that Peruvianus was more potent than Pachanoi, but I just read this:
A Look at the Mescaline Content of T. peruvianus and T. pachanoi
Considering these findings I'd personally go with San Pedro, since the spines are much smaller than T. Peruvianus', thus making it easier to prepare. Speaking of which, I wouldn't go with a tea, since drinking it would be nasty and may lead to vomiting. Both of my successful attempts at using T. Pachanoi involved these steps:
1) remove the spines without removing too much of the meat, discard
2) peel off the tough, waxy skin (also without removing too much of the meat)(takes a while, but it's part of the experience) and discard
3) cut the core away from the meat and discard it
4) blend the meat thoroughly in a blender until it becomes a voluminous, slimy foam
5) transfer slimy foam to a cooking pot, optionally adding some lemon juice
6) boil on low until mixture is no longer a foam, and most of the water has evaporated
7) transfer to a cookie sheet and bake in oven at low heat until you are left with a small amount of a baby food-like substance
8} swallow in small amounts, tossing it as far behind your tongue as possible and chasing with a bite of bread each time
I have never thrown it back up using this method, but I was careful not to eat or move around much until the effects were coming on strongly. It's a wonderful cactus; I'd love to try it again. Unfortunately, San Pedro doesn't grow too well at my elevation (not without a greenhouse, anyway)
