I'm not sure if many know about this website, because it's in German, but I've been using it for a few years. They review many different keyboards (including the Kurzweil PC3 series and Roland's Integra-7. They give a rating for each from 1 to 5 stars.

If you want to read it in English, simply translate it on Google Translate, or click on Translate when you Google the website. I post this to allow you to hear actual recordings of the keyboards' sounds and styles. If someone is considering both the Korg and Yamaha, this might help them decide.

Korg Pa4X: http://www.bonedo.de/artikel/einzelansicht/korg-pa4x-76-international-test.html

Yamaha Tyros 5: http://www.bonedo.de/artikel/einzelansicht/yamaha-tyros5-76-test.html