In my opinion, MiniLab MkII has 80% of the Keystep + Beatstep functionality. You'll miss the extra 8 pads, (but you have the 9-16 pad switch), dedicated transport control, the extra control knob, and the builtin sequencer (not much use if you have a DAW), but you have the advantage of a compact setup.
I'd buy MiniLab MkII first, and if not enough, I'f add a Keystep later.