Roland and Ketron can play 3 patterns per part (Maj / Min / 7th)
Korg it's 6 patterns for Mains, and 2 for other
Yamaha is, as Jorgen saied : you can record 16 tracks per part.
Then you decide witch track will play with witch chord pattern.
So you can for example share the drums for all patterns, but decide to record another bass track for minor chords...
Which makes yamaha styles more versatile..
but then i think all major style formats have more then enough to offer almost all players... So the only thing that counts is the quallity of onboard styles... but also the number of high quallity user created style files that are on offer for free, and the number of high quallity sound and style expansions sold by the dealers.
And for the more daring musicians, the ease of use for creating your own high quallity styles.. tough i prefer to edit styletracks on a computer..and then export them..