The PA-50 has some pretty good organ sounds, Most performances and OTS organ presets have a leslie effect preconfigured (You can use the joystick to switch between slow and fast).
For its price, The PA-50 is unbeatable, Nor the PSR-1500 or the EXR's compare IMHO.
It has some really good voices in each category, some don't like the piano that much, its a little bright/harsh sounding.
I personally prefer Korg's styles above any other brand, the styles are generally very contemporary sounding, and are also a lot longer and more varied than Yamaha's (Korg's styles are generally 8 to 16 measures long, Most Yamaha styles aren't longer than 4).
But let your own ears be the judge, We all have different tastes.

Greetz ,
Marcel