I seel both keyboards at my store in Los Angeles, Ca. As for the vocal harmonizers I would give the edge to the Korg. It's using a TC Helicon chip inside which does a fantastic job. As in both the Yamaha and the Korg, both harmonizers feature extensive editing capabilities but I find the Korg a bit more natural in the way the harmonized parts follow the chords played and lead vocal sang. As to the sounds and styles, they are both outstanding. If you wish to do more sampling in a keyboard, the Yamaha offers much more memory potential (1GB vs 32MB). The synth editing on the Korg is like the Trition however, 6 oscillators (wave forms) can be used in any 1 voice which allows for an lot of editing potential. Sequencer wise, they both have 16 tracks but there is a difference in the way the two work. Korg uses a backing sequence to record the style and then you add the rest of the tracks in the 16 track seq. mode. Or, you can start in this mode, one track at a time. The Yamaha has a different approach, where you can record any thing you can play or push a button and each track defaults to a different part in the 16 track seq. Next, if you want to add more tracks or just record one track at a time, you must select a track and select a part you wish to record on this track. So, if you want to keep recording a single sound at a time, you must keep assigning the part called "R1" to each track as you go. If not, your part defaults will screw you up until you figure this out.
I like the PA1XPro model better than the PA1X. It has 76 keys instead of 61, no speakers compared to the 61 key version, so it is lighter in weight. It comes with a hard drive already installed out of the box. You have to add one in the PA1X. The keys are larger and nicer to play and it is much more popular with musicians.
The Tyros 2 has 61 semiweighted keys and there is no 76 key option. No hard drive comes with the keyboard and you would have to add one if you want to do hard disk audio recording.
With the Korg, you also need to add an MP3 recorder chip option and you can add a CD burner option if you wish.
Some might choose one over the other for sounds, some will choose the Yamaha for it's articulated voices, some will choose the Yamaha because it has 4 fill ins and the Korg has only 2. The Yamaha has 128 note polyphony, the Korg has 62, but this has not been an issue because of the way Korg works around voice allocation. Nobody has complained that I'm aware of.
I hope this helps. In my opinion, both are sensational choices and around the same price.

George Kaye
Kaye's Music Scene
Reseda, California