Biggest reason is BES support instead of ActiveSync. BES is true push email, while ActiveSync is a weird hybrid push/pull email solution. BES uses much smaller amounts of data and works much quicker, in addition to BES reporting features, policy control (remote locking and wiping of devices if they are stolen and the like). BES and the Blackberry offer a much more seamless corporate email solution than Apple does. That being said, the Storm is probably the Blackberry I'd like to get the least (the Bold is what I'd much rather have). The other apps on the Blackberry work better as well, with less application lag, less crashing, and better overall "work" tools. This is why I said the Blackberry is far ahead.
From the standpoint of a phone that is also an entertainment device, if this is what you are going for, Apple wins. They obviously can't match the gaggle of games and entertainment devices the iPhone offers. But until the iPhone catches up on the productivity end, they won't compete with the Blackberry - and quite frankly they haven't really tried all that much to do so.