I have to preface this that I would really have to try one of these out in order to make a complete judgement of Ketron.
But, having said that, everything I've heard from them, and speaking as a drummer, these drums are way too much in your face, too loud, overdone and overpowering and overochestrated. Quite unatural. Any band I'd ever played in or heard the drummer would be told to back off if they sounded like that, both in volume and in being too busy.
As far as the horns and solo instruments, to me, it sounds like old outdated synthesizer type of sounds. I was selling Technics products in the late '80's and I feel Ketron does not sound as good as that 30 year old technology.
I am saying this only from the online demos I've heard. I'd like to see what it's like in person.
I feel Yamaha has got the best voices out there. It would be interesting to try Ketron drums with Tyros voices, with the drums toned down. Then again, I need to hear what the T4 drums sound like in person also.
Yamaha, to me sounds more real and easy on the ears and not so frantic.
IMHO