Being a die-hard Yammie fan, whenever I had a chance in the past to play a Korg Pa, I hated it. Always thought it was difficult to navigate the menus and find the sounds I wanted. (they have no rhyme or reason in categorizing within the voice categories. You'll find a premium voice, followed by a GM voice next on the list, followed by another version of a premium voice)

Going from a Yamaha OS to Korg is like night and day. You really need to spend time - a good deal of time - with a Korg to learn to appreciate it's depth and versatility. Now that I own a Korg (because I spent hours playing a couple Pa's before buying one) I must say I really, really like what Korg does. However, I really, really like Yamaha too.

Fact is, IMO, Yamaha boards have a much easier learning curve - maybe because most of the line is geared toward home players.
Korg is an acquired taste, but worth the trouble learning (again, IMO). And Korg only produces a few arranger models. - geared toward pro use.

Now that I own both (Pa500 and S910) it's quite an interesting combination of OS's, styles, and voices.

Now all I need to do is add a Roland to the mix!

Tim