Yes I know I´m sick and I´m searching for professional help soon. Two weeks ago I replaced my Psr 1500 for the Psr s900 I longed to own. Due to Yamaha very high prices in my country first I bought a Pa500 and later the Mediastation for Vsti. As many of you know I use all my keyboards together mixing the different textures of sounds, but of course, my Psr 1500 is on sale now in Argentina. Comparing both the Pa500 and the Psr s900 side by side with same monitor speakers I can definetly say Korg is by far more live and crispy and the drums are 100% better.In the Psr I can't get the same sound quality for the drums even tweaking all the EQ parameters (for sure I know all the tricks in the Yamaha after 3 years playing the PSR). However the SA and special voices (Sweet, Cool, Mega) are excellent and I can´t reach the same realism with the Pa500 so easily. In my case I use the Pa500's drums when I play the PSR's styles which may not sound properly only with some drum kits (ie dance or brush kits) so in that case I mute the Pa´s Drum channel involved. Not even comparable is the Pa´s capabilities for editing sounds (EQ of individual parts, waves etc) contolling ext. keyboards, setting split points, velocity etc to the right/left hand parts and so so so...
But... I love Yamaha! It´s not better I know and that's why I couldn't do without Korg after knowing it. I think the reason I love Yamaha is because first of all I am an amateur (to whom the product is mainly focused and they know what I need) and because I grew up loving Yamaha since I was a kid. Check the manual and see how simple they make everything, sometimes using some drawings for kiddies. So it's a very intelligent and trustful company which has been working and growing with their customers.
That's the reason why many people love Yamaha: it's part of our own lives and story the same way many people prefer Coke over newer brands even more tasteful.

PS. Sorry I am always late commenting older products. I know the Psr s910 is already there but in Argentina things arrive 1 or 2 years later if they ever do, and yes... I paid Us$2400 for this one and the Congress has just approved a law which might increase imported electronic products over 30%. A cure for my desease?