There is no doubt in my mind that Tyros is better than PSR3K - it would be a real shame on Yamaha if there wasn't a difference. I bought PSR3K because music is my hobby, not my profession. It comes close to the Tyros and they have compatible styles because of the megavoices.
Aftertouch is one thing that I miss on the PSR3K and the other thing is 3 layers for the right voice. With three layers you can make the voices sound more realistic.
I don't know about a better soundchip in the Tyros though. If you want to do an honest A/B test, you have to use the same voices, styles and the same soundsystem at the same volume. And if there is a difference, maybe you can hear it only through a very pricy soundsystem. But if you are a pro, why settle for less than a Tyros? It looks better on stage too. There is no shame in using a PSR3K too, even for a pro, but the Tyros surely looks much better.
Anyway I am enjoying my PSR3K.

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drdalet