I'm in the same boat as brewster, having done mushrooms and San Pedro, but never Ayahuasca. I'm not sure the exact numbers, but I did shrooms about 50 to 60 times. And I've done San Pedro 20 something times now, probably about 25. I've also done LSD and a few other substances.
The main difference that I find with San Pedro compared to the tryptamines is that San Pedro is much more of a mind AND body experience. The duration of the experience is longer. The bodyload is more intense. The effects hit you in waves throughout the experience. There is a mental clarity to the experience compared to the tryptamines (which can be confusing and foggy at higher doses). The visuals on San Pedro are much more concrete and realistic. For example, on mushrooms there were many times when I was not really sure what I was looking at. Was that a balloon that passed by in the sky, or was it a blimp, or was it an alien spacecraft? The visual representation of that object appeared to change as I looked away and looked back at it. With San Pedro the visuals are very vivid and clear and detailed, and the visual stays what it is without morphing, even though there is some movement. Its hard to describe.
I guess I'm rambling at this point. Another difference is that there is a palpable afterglow effect from San Pedro that lasts for days or even weeks. There are many differences, but also similarities too. Its a very good medicine. From what I understand (though I have never personally experienced it) many of the ceremonies in South America are traditionally conducted at lower doses. When you up the dose with San Pedro the effects (especially visuals) increase dramatically, and the duraution goes quite a bit longer. But there can also be significant nausea and muscle cramps and other challenging physical side effects. At very high doses the trip can last 20 or more hours.
Its definitely worth exploring more and going deeper if you get the opportunity.