Triton Classic: 32MB PCM ROM samples, 16M RAM expandable to 64M, 62 voices in single mode/31 in double-mode, 640 programs total, 2 PCM ROM expansion slots.
Triton Studio: 48MB PCM ROM samples, 16M RAM expandable to 96M, 60 voices in single mode/30 in double-mode (this DOUBLES if you have a PCM ROM board so its really 2x what the Triton Classic has), 1536 programs total, 7 PCM ROM expansion slots, 5gig internal harddrive comes standard, SCSI controlled comes standard, digital i/o comes standard, 6x faster processor than the Triton Classic, 6x faster touch-screen, WAY better converters.
Thats the basics just off the top of my head but there are plenty more. Basically Korg released the Triton, listened to all the user feedback and made the Triton Studio. The Triton Classic is still a very capable workstation but the Triton Studio pisses all over it if you want the honest truth.
My $.02 worth of first-hand experience with both.