Well I prefer the Fantom too, Its hard to judge the Motif by listening at the demos only, But the Motif, like almost every other Yamaha synth, shared one bad idiosyncrasy, and thats its canned and synthetic sound, Every time I hear a Yamaha I can clearly hear that, its like a typical sauce greased all over their sounds.
And I honestly dont get those people who just say "You can't go wrong with Yamaha", thats not true, You CAN go wrong, I was so full of confidence that the PSR-2000 I tried had to sound fantastic, But I was greatly dissapointed when I heard it live, also tried the Tyros briefly, and sounded a bit better, but it still was a dissapointment.
Its a pity cause Yamaha has almost everything right except the sounds.
Just my opinion, No offence...

Greetz ,
Marcel