Hi Spalding
Styles like sounds are very personal and my order of preference is:

Roland
Wersi
Korg
Ketron
Yamaha

Now because I have placed the Yamaha last, does this make it a bad arranger, absolutely not, it’s just that it doesn’t give ME the impression that I am listening to a live band.
Does the Roland being at the top mean it’s the best arranger, No, it just means that I find the styles to sound more real then the others.
You ears prefer Korg and Yamaha, however it doesn’t make them any better then the others; it’s just YOUR personal preference.

BTW in case you are interested, sound wise my personal preference is:

Wersi
Korg
Ketron/Roland
Yamaha

Again yours will probably be different. (However it still doesn’t make one better then the other)
Regards

Bill