I bought the mopho keys a few months back. It is awesome. The build is amazing. I’ve owned a lot of boards with aftertouch and the mopho was the first one that responded the way I always thought aftertouch should. It makes a great controller for the A4 too. The sound is great and records well, sits in a mix well.
Haven’t had a chance to play the BS2. I do own a sub phatty and minibrute too and if I had to make sacrifices , The mopho would be the one I held on to.
fwiw