If this helps ...
My reason to buy the Motif was as follows (considering I have other keyboards)
- sound quality - the primary consideration as far as I'm concerned, and yamaha has the choice samples nowadays.
- the sampler of 4 mb can be expanded to 64mb, so its ideal for sampling studio produced material which needs to be performed live.
- space for 3 more expansion cards.
- scsi port, and 6 assignable analog audio outputs as well as optical and S/P DIF digital outputs, which makes recording easier and higher quality compared to other makes.
- easy to use control surface.
- MIDI sequencing on-board.
All the above ment, for me, that the motif is the best writing / production tool. I can basically write whole songs on it, then take it to the studio, track what I need to keep at a very high quality, and have parts ready for all others to play. Then, when finished, I can sample sounds from a finished recording and program them in the motif, to play live.
http://www.yamahasynth.com/pro/motif/ is the best motif info site, I think.
Another good option to buy now is a used Korg Triton. Plenty for sale, as many people are swapping them for motifs.