Different drugs for different purposes.
Shrooms are a classic, typical psychedelic. Good for all cases in which a psychedelic is appropriate.
aMT is a long-lasting psychedelic/empathogen, which causes physical sideffects in some individuals. I'd say it's suited for entirely different sorts of experiences - It would, i think, work better as a rave/club drug than shrooms - assuming it didn't make you sick (I don't get nausea from it, but a significant portion of people do). It is not a general purpose psychedelic like shrooms, acid, etc. I havn't explored it at full doses, but it is qualitatively different - and also inconvenient to take, due to the fairly long duration - I'm inclined to say that it doesn't go as deep. Visual effects are more mild and qualitatively different than shrooms.