Emu XL-7 & MP-7 User's Group

Both are a mixed bag.  Capable bread and butter romplers with both good and bad sounds scattered throughout.  I had both in an MP-7 for a while and had a huge selection of sounds.  

I prefer the ZR simply because it has a couple of string sounds and a bass guitar wave that I find very useful so I took out the Composer but either would have worked fine for me.

If you must have pianos then the ZR may suit you better.  It is a fair leap better than anything on the Composer or Phatt.  It's not great but is works well in any given pattern.  I'd say it's about the same quality as a Nord Electro 2.  Neither are particularly good for solo piano work but both sit well in a mix.

Also: with either of them in the MP-7 I really had little time for the Phatt Rom other than for some kits and synth sounds.  If you have the cash, I'd store away the Phatt (keep it for resale value of the MP-7), pick up either the Composer or ZR and save up for whichever specialized ROM suits your music best.