If you take BES out of the picture (yes, not all companies have it or support it) then the iPhone does make a better enterprise device.

I came from a iPhone to a Blackberry curve (just to try out, but reverse from the OP). It just so happens that I prefer the blackberry now and I'm sticking with it for the time being.

As far as enterprise features are concerned, I had near full MS Exchange capabilies with the iPhone. OTA contacts/calendar and complete mailbox syncing (even old emails). Tasks and to-do's did not sync, but I never used them so I didn't miss out on it. The blackberry on BIS doesn't even compare. 15 min poll for email and I have to connect the phone once a day to keep stuff my contacts/calendars in sync. No folder management, no old email syncing.

Apple's app store is amazing and the iPhone can do some amazing things for a phone. The browser is the best I've ever used on phone. Typing on the virtual keyboard takes time and there is a learning curve. I type faster on my old iPhone than on my blackberry.

Why did I stick with the blackberry? Better camera features, MMS, video, SMS forwarding, copy/paste, turn by turn navigation and a few other features that I need that the iPhone doesn't offer.

Both phones are great. You just need to figure out what you feel you need most out of a phone, compare them and pick one that suits you best.