Korg Pa4x still suffers of bad retriggering notes if you don't push fill buttons or change chords at exactly the CORRECT time. This has always been a problem of korg arrangers, Roland was better on handling this. I didn't ever tried a Yamaha arranger so I can't tell about Yamaha arrangers.
Yamaha is perfect in timing.Even if you trigger a little early , it will trigger in sync with the beat. All fills and breaks. The complaint by some is "it's too predictable".
We'll, like predictable, I don't like unwanted surprises, especially with fills and breaks too late or too early.
I think it's the coding when they program. Someone (IT expert) from this forum once mentioned that Korg and Roland use a similar coding for styles and Yamaha uses the other.