One has a large screen and full qwerty. The other does not. One will fit in your pocket and other most likely will not. That's about it. It's all about form factor not function. One is SureType the other is QWERTY.
My curve actually fits in my pocket. I just choose not to put it there since I want to keep it nice.
I traded my pearl in for the curve. The differences to me was the keyboard. I didn't like suretype,and I know there is a option of turning it off I just wanted a full keyboard.
Also the screen size. I like having a larger screen without having a bulky phone.
I compared them both online and the curve is really no more than a half a inch wider than the pearl. (correct me if I'm wrong please) so that was another factor in me making the switch. I had thought the curve was some big brick,lol.
Go to the store and check them both out. I believe their both capable of doing the same things.(Except maybe wifi,is that right?lol) Just a personal preference in which suits your needs better.