Played one for about an hour at Guitar Center. I have a Motif ES for many years and know it's sounds intimately. I heard a lot of similar sounds between the two boards, although the MODX does have a few new sounds that are excellent. Mind you I focused on Guitar, organ, bass and EP and a few string sounds. I dabbled a bit with some other sounds, but not long enough to get a good feel. Perhaps there are bigger differences there. The feeling to me that the two sounded similar is not a bad thing at all. I love my ES to this day. If I no longer had it, I'd seriously consider this board. All in all, it sounds excellent.
I also own a motif xs rack..
And a modx
Yes many sounds are the same, but i found quickly that the new sounds have become my goto sounds on the modx, they are hugely better..
Add to that the linitations of only 4 sounds in a performance on the ES and the huge improvement in numbers as well as in quallity of the dsp, and its obvious why the modx at its current price is the new king of yamaha..
The organ sounds are for exampke vastly improved and finally sound like a b3..
The main piano and dp sounds are of a different galax, then the es ones
And then the es does not have any AEM (super articulation) which makes arcoustic sounds with element swtching sound much more realistic.
Just my opinions.. based on owning both the motif xs and having owned the es, and also owning a modx