Don got it right.
Dromeus I need a band(or a an orchestra) to play with me,so every other kind of instrument it doesn't suit me,even if it is a 45.000$ Grand Piano.
Both Yamaha & Korg have overall great sounds.
Both have a piano sound which is weak compared to a digital piano no matter how many gigabytes someone will spend to create one.
Their difference is in amount of the available styles.
I have done my homework as Don said and looked up for styles to see If I could play my favourite music before I buy a Yamaha.
Why is it so hard to find covers with specific songs and song styles from Korg players?
How an upgrade or two or three,will be useful too me in the first place,
if I have to make my own styles for well known songs while there are players who find it hard to change the OTS settings?
Let's see... a few of the song/styles I use on my 4x...
Suspicious Minds
Wonderful Tonight
Heartbreak Hotel
Hound Dog
Long Train Running
Mustang Sally
Midnight Hour
Many Credence songs
Now or Never
Crocodile Rock
Twist
Have You Ever Seen the Rain
Pretty Woman
Satisfaction
The Last Waltz
Last Date
Gimme Three Steps
The Weight
Black Magic Woman
Tears in Heaven
Lay Down Sally
Shake a Tail Feather
Soul Man
Chain of Fools
Rock Around the Clock
Johnny Be Good
Candle in the Wind
Too many to remember actually. Many are factory styles, some are extra free styles from Korg, some are from the German model "Musicant", some are from older models.
Plus, all you have to do to get a song specific file, is load the midi file, push a button to automatically convert it to a style.
Not all conversions are perfect but many are really good.
Now the later "dance" songs, rap, etc., I don't know about. I know there are some Disco styles that fit specific songs.
Many or maybe all of these styles and more are available, in my PSR as well.
I wouldn't think availability of song/styles would be a determining factor in choose which arranger to buy. There are many more strengths and weaknesses in both lines.
I think we are getting off topic here, so will bow out unless asked something specific.
Oh, and I preferred the PA4X, before either one of the upgrades, but you understand my needs and likes will almost certainly be different from others.