DS and FA are identical in this respect... you can split/layer up to 16 sounds, with as many different split points among them as you want (because each sound has its own definable key range).
There's no right answer there, that's always subjective, but each has some "technical" advantages over the other, sonically. The FA has the "SuperNATURAL" VA synth, and a handful of SuperNATURAL acoustic tones as well. OTOH, the balance of the sounds come from the XV-5080, whereas the sound set of the DS is not as old as that.
On my ds-61 it seems to have just upper and lower split. Is there a menu function, edit etc to get more splits?
Also the fa has chord memory which I used to find handy as I'm not a real keyboardist, just a dumb bass player
Also the sounds just seem to be bigger with the fa series, I really like its fake electric guitar sound as well!
Just getting back into adding keys with bass in my band..now that bands are playing out again! Hurrah!
Thanks for being patient with my stupid questions!