Yamaha definitely has the edge with the number of styles available, probably because they have sold a heck of a lot more arranger keyboards and thus have a much larger userbase! Recently, I purchased a Roland GW-7 and discovered several collections of compatible styles: factory styles from the new Roland EXR40 Oriental Arranger, Roland G1000 conversions from Yamaha's PSR9000 & Tyros, conversions from Roland's VA series, Solton X1, Korg i30, Technics KN\KR series. I also decided to bite the bullet and buy EMC Style Works 2000 in order to have access to styles from the best arranger keyboards. After using the demo version, seeing exactly how it operates...it's a no brainer! Definitely a worthwhile investment! Also, I need to be able and edit styles so I can fit the maximum possible amount of style data in my keyboard's limited flash memory.
Michael