Size. I'm in the same boat. I've long considered getting a used Pearl as a backup, but never pulled the trigger. Depending on the price when it's available stateside, I may get one, even to use full time.
When I bought my Curve, the spell check, better camera, and general improvements were as much of a factor as the full keyboard. I played around with SureType for a few minutes and found it to work okay and I'm sure I could get used to it given time. So I'm not opposed to not having a full keyboard.