I entirely agree with Donny here. If you do not tweak your arranger be it a Genos or whatever you will probably only use 50% (tops) of its possibilities. The Songbooks in the Korg are notorious to me for being lacking. I am always under the impression they are a last minute addition and sometimes wonder if they are not created at random by some computer program.
Sounds ( how many does one want, I mean let's face it over 1700 sounds on the Korgs, totally absurd and ridiculous. Who needs 20 piano's if they all go back to the same samples ?) Worse even in other departments. Surely most of us could get by comfortably with say 200 truly outstanding sounds, shall we say 10 of 15 in each category ?
STYLES: yes Yamaha has got so many styles that you cannot see the wood for the trees and in particular Songstyles, which personally I do not like cause they ain't very creative. I do understand though that the gigging entertainer has to please his audience and therefor has to come up with a song as close to the original arrangement as possible. But then again, I would guess that for the Yamahas only you could probably have your pick from a score of songstyles for just one famous song such as My Way, etc.etc. Mind you I am not knocking it, hey it that is what you want, that is what you can get. But if you want to be original or sound different from the masses you will have to customize your arranger keyboard and also, daringly, present your audiences with an arrangment that shies away from the original, the latter 99 times out of a 100 being better than your version anyway.
Currently I must have approx. 900 styles in my Korg PA1000 of which over 600 original Korg styles. To me that is amply sufficient. There is not much lacking and if I had any wishes left it would be for the acoustic piano and the spanish guitar to sound like the yammies, other than that I am settled

regards
John