HUGE Difference. Cell phone provider's give limited access to browser capabilities since most of the cell phone data plans are really cheap and are unlimited.
On a cell phone you can mainly browse to the links that the cell phone provider puts on their WAP Portal. Yes they would include the most basic functions such as checking your mail (hotmail, yahoo, gmail) and of course Facebook.
But 90% of the times when you try to browse to a normal site it wouldn't work. if it does awesome! If it doesn't then the provider doesn't support it.
On the other hand Blackberry's internet is a real internet on your phone. It is only limited by the website's inability to work properly on a data devices. However, 90% of the wesbites would work flawlessly.