Eh bk-2C-B is lovely but it's like a longer lasting more pleasant 2C-B high with a slightly uncomfortable comedown period with muscle tension and such. Generally I'd take it over 2C-B for a longer party, and take 2C-B over bk-2C-B for a shorter party, it's not an MDxx like really though and is more an empathogenic psychedelic.
aMT and MDxx don't have as much in common in terms of feel - aMT is my favourite psychedelic though hands down and cured my social anxiety in my first trip on the stuff, been 2 years and 5 months since then and I'm still anxiety free.
It's a wonderful drug but it's a psychedelic with an empathogenic effects rather than an empathogen with psychedelic effects, if that makes sense - it's very different from your standard roll, but if you like both psychedelics and empathogens you'll love it, it's kind of between something like MDA/6-APB/5-APB (psychedelic empathogens) and your traditional psychedelics like LSD and Psilocin.
5-MAPB on the other hand substitutes well for MDMA and feels very similar, not identical but very close.
That said all of the 3 are amazing drugs, just if you're looking for something that feels like MDMA, the only one of the three that does is 5-MAPB, while the other two are unique lovely psychedelics, bk-2C-B has that 2C-B like empathy to it but I'm certain isn't a traditional monoamine releaser just as 2C-B isn't, then aMT is a psychedelic that's also a triple releaser like MDMA - and 5-MAPB is your MDMA-like triple releaser with similar effects.
If someone were to ask what kind of drugs a psychedelic and empathogen lover would like, then I'd say all three fit the bill, but if you're asking for the closest RC to MDMA, 5-MAPB is close, while the other two are completely different drugs, with their own wonderful pros, but the experience isn't like MDMA really.