PA3X has SO many useable styles that I've only had to stretch a little for just a few that I needed. They were easy to find or make. Some styles are song specific, but most can be used for a wide variety of songs.
I agree that Yamaha has the edge in solo sounds, but to me, that's about where it ends. Features I enjoy more on the PA3X include drums, bass, styles, vocal processor/harmonizer, mixer, songbook, touch screen, build quality, facility for dedicated (yet lightweight) foot controller, XLR input, tons of programmable slider/buttons/switches, chord sequencer, effects strip, and I'm certain I'm leaving out stuff.
I'm very happy with my Korg, but it is not the PA600 of course, so it would be an unfair comparison to PSRS950. It WOULD be a fair comparison to Tyros 4. On T4, I prefer the screen (would be better if it were touch), ability to audition new styles easier, and many of the lead sounds.
There's also a long history of free upgrades that Korg usually does and the periodic release of FREE new styles.
Easy choice for me!
Having said all this, I could happily work with any of the current totl arrangers, or even motl.
My plan is to get an S950 for my backup keyboard, if I don't change my mind before they are available.
I spent today tweaking my PA3X, making a few more songbook entries, experimenting with some of the many setups in the Performance banks, etc. I have barely scratched the surface of its capabilities!
DonM