This site both offer comparisons of features along with some technical information. Some aspects are very subjective based on a user’s preference, so you might want to head to your local cell phone store and check them out for your self.
As far as I know, the 8330 is 3G and has 96mb of memory as opposed to the non 3G 8310 with only 64mb memory.
Hope this helps!
The Blackberry which is better is the one which is better for you. Personal I prefer my 8830. It’s got a full keyboard, plays MP3s and videos, and has room for an SD card. It doesn’t have a camera so that I don’t have to worry about not being able to take it into a data center or other secure location.