I carry a BB Curve for business and the iPhone for personal use so here's just a few reasons off the top of my head:
End user features:
- iPhone currently only supports Microsoft Exchange. It misses the other 40% of the market who use Lotus Notes or Groupwise. (Although Domino 8.5.1 is slated to provide Exchange ActiveSync support)
- no support in iPhone for corporate instant messaging solutions like Sametime or Office Communications Server
- Battery lasts longer on the BB. If I go on a overnight trip I don't have to bring a charger, the battery easily lasts 2 days even with heavy usage. I can bring along a 2nd battery if I need to - no hunting for power sockets at an airport!
- Extra loud speakerphone that doubles as a makeshift polycom for all your colleagues when stuck at a remote customer location
- Profiles that let you totally silence the phone quickly so it doesn't distract you while you're up there giving a presentation. Vibrating pants are not cool
- LED light to let you know you have mail even if its on total silent mode
- Camera-less versions available for folks who work in high security locations
- Reasonable international data roaming plans e.g. $64.99 for unlimited international BB data on AT&T
- BB devices available on multiple carriers and networks for maximum coverage. AT&T has serious network congestion issues in some locales e.g. NYC and parts of southern California
- Bluetooth voice dialing, very handy when you're driving from the airport to the hotel in strange city and trying to make calls while negotiating rush hour traffic
- Telenav for driving directions in unfamiliar places
- Ability to open files in ZIP attachments
- BB Messenger. Instant and always-on. Like SMS text messaging without the per message charges
IT Admin features:
- One single place to manage everything, the BES server. With iPhone you'd use Exchange for policy management, IIS for logging, Apple policy config tool for device management
- Unable to forcibly push policies on the iPhone. Users have to manually click on a email attachment or run the policy to add it to their phones. Also unable to update policies OTA
- Very fine grained security control for Blackberry (you can enable/disable almost every feature in the device). iPhone supports very limited Exchange ActiveSync policies e.g. remote wipe, and disable camera (only with Exchange 2007)
- Admins can prevent users from installing apps on a BB
- No good reporting and logging tool for iPhones