To complement the info by Gary....besides the new S.A. sounds, there are lots of new Mega sounds too, and do not forget that most of the styles (260 in the PSR3000 vs. 400 in the T2, so it has a lot of new styles with the new voices), and the styles that are similar in the 3000, have been "re-voiced" and re-arranged to show off the T2 sounds. Check the Modern Big band, the Cha-chas (the intro 3 in the organ Cha Cha has a troumpet not available in the 3K), etc, etc.
I made that transition when the T2 came out almost a year ago, a few weeks later I sold my 3K.
Now I am waiting to pair my T2 with the New Korg PA 800, as a former organist, I need 2 boards for my playing style and I prefer 2 arrangers (different brands of course).