If you haven't used a BB before, you might not have trouble with the Pearl keyboard. I've used PDA phones with full QWERTY keyboards for so long I couldn't go back to a 2 or 3 letter per key phone now. The Curve is a little larger than the Pearl, yes. My brother does like the size of the Pearl.
Who is your service with? If you have a SIM card I believe that they can transfer your numbers, but transferring from a non-PDA to a PDA type phone hasn't always worked for me in the past. I've always been able to turn my old phones on, but without a transfer method like Bluetooth or some type of connectivity the pics and texts on the old phone were stuck there. The PDA phones can be synced to your computer and the pics can be stored there, but I don't think the Katana can be synced like that.
Of course, I may be wrong. I've had a lot of phones, but am by no means an expert.