I havn't got a Yamaha yet, but the fx/ dsp functions shit all over Akai/ Emu's.
I've got an emu ultra and thinking of getting the new Yam when it comes out.
Personally, i think Emu/ Akai are fine for all types of music especially Orchestra, film etc... But the Yams are great for cutting edge music.
When i sample, i want to manipulate, not just to playback and filter. That's what makes the yams so appealing to me.