The Kronos uses the STR 1 sound engine which is designed specifically to model plucked stringed instruments. (It was also on the OASIS)

You will find demos here http://www.korg.com/product.aspx?pd=214 (Ckick on the STR 1 demo) and as you will hear; its flexibility is way beyond anything the T4 sample layer switching can ever hope to achieve.

The difference between the 2 being that you have to set up the Kronos yourself, whereas the T4 does everything for you, thus it is easier to sound great OOTB with a T4, but severely limiting when you want to make something your own.

That essentially is the difference between a Workstation and an Arranger.

Bill