The PSR 2100 has more User Memory, more Wav Rom, more Voices, more Sweet! Live! and Cool! voices than the PSR 1100 or PSR 2000, USB connection (so does the 1100). Other than that, it is basically the same animal as the PSR 2000. IF you want a "break out of the mold" Keyboard, do yourself a favor and get a Tyros. I own a PSR 2000 and it is a great little Keyboard but when I bought a Tyros my PSR 2000 has significantly shrunk in magnitude to what I thought a good Arranger Keyboard was. If you're short on dough, the PSR 2000 or 2100 would be an excellent choice though for a mid-range Arranger Keyboard.

Best regards,
Mike