Korg has way more assignable sliders and knobs.
The vocal harmonizer is miles better than Yamaha.
The drum kits, with the exception of audio ones, are much more realistic.
I find the gimmicks on many of the Yamaha guitar sounds put stuff in at the wrong times. I prefer to do it myself.
Korg has the EC5 multi foot control which is light in weight, inexpensive and totally programmable. Yamaha's only option is the very expensive, very heavy, MFC10. The Tyros does have 3 programmable foot pedals, but the PSRs only 2.
I of course have not played a PA4X, but the 3X, although similar in weight to Tyros, is a much more manageable size, and is far easier to lift off the stand, put in bag and transport.
I would not use the organ world and ensemble sections, although I can see where many might. I want to sound like a small combo, not an orchestra or movie score, or most of all a big organ.
There are positives on each side I'm sure we're overlooking, but at least for me it's an easy choice. And isn't it wonderful we have so many great choices!!