I chose Yamaha because it has the MOST available styles. If you cannot find a stylr you need in Yamaha's library you won;t find it. The Yamaha library is extensive and has a huge support base of websites and people that create styles. AS far as sounds go, Thats a subjective area. Either you like the "signiture sound" of a Manufacturer or you don;t/ They all have their own idea of what a flute sounds like, or drums, bases on and on.

Yamaha samples their own Pianos, horns as well as others. My wife preferred the Roland Digital Piano for years. Now shes torn between the CP300 and her RD700. I am not as astute aurally. I can make one sound like the other using post recording tools. She's a live player, IM a Studio Rat. After having a PA2x and now a Tyros 3. I prefer the sheen of the Yamaha sound over the "live" Korg sound. But I rarely just use the Yamaha voices in their own styles.

The Yamaha has far less "features" meaning its easier to get up and running. You really have to hear the M3 then the Motif and Fantom to get an idea. most MI stores wont carry TOTTL Arrangers.