I decided for a Yamaha MO8 (no X here), because of the excellent keyboard. I am a piano player too, and like to have that feel. The Korg and Roland equivalents were OK, but not as good as the Yamaha. I am using it as a MIDI controller for my virtual instruments as well as a sound device, because some sounds in it are still superior to what I find in my virtual instruments.
And I can't think of anything that a MIDI Controller keyboard can do that a MOX8 does't.
Too many options kill creativity.