Both keyboards have their issues. Typing numbers and special symbols on the BlackBerry can result in hand-wrenching positions, and you need to use both thumbs, due to how the Shift key works. Entering numerals with regular text is particularly a pain. I also can't read the symbols on the BlackBerry keyboard without my glasses. The iPhone works best when tapping with one thumb, though I still have trouble with Q, W, O, and P, due to the optical illusion as to their location caused by the glass.
For the rest of the UI -- the screen size, the navigation, and option selection -- the BlackBerry is torture. That little roller ball is hard to control precisely. The menus can be difficult to scroll through. Everything just takes longer to do. Apple's UI is elegant and easy. Its mouse-like touch navigation coupled with the use of gestures makes it easy to delete items, select multiple items, scroll, and enlarge and shrink screens. Its use of a consistent set of input controls for dates, lists, and so on lets the UI become second nature quickly.
On a BlackBerry, the screen is hard to read, hard to navigate, and hard to zoom, and it's often covered by the menus. The UI for input controls is inconsistent at best. Clearly little to no thought has been brought to the BlackBerry UI; it's just a Frankenstein collection of methods developed in isolation from each other. Apple's real UI advantage is not the touch interface (though it works wonderfully in a graphical environment), but something less tangible. It's the well-thought-out, consistently implemented UI that leaves the iPhone unmatched.
In other areas, the iPhone's rotation ability and its use of accelerometer for motion detection allow uses -- some silly, some practical -- the BlackBerry can't even dream of.
As for the devices themselves, I found myself accidentally pushing the BlackBerry's camera button a lot, and the lack of autolock for the keyboard meant that I often had my address book or other function active when I took it out of my pocket. The iPhone's buttons aren't so easily pressed by mistake, and its easily set autolock prevents accidental 911 calls and address book edits.
One big drawback of the iPhone had been its lack of copy and paste, which iPhone OS 3.0 addresses in a very easy-to-use, intuitive approach. It's far superior to the BlackBerry's key-and-menu-based approach; plus, it can handle graphics and regions of Web pages, not just text. That former BlackBerry advantage is no more.
Where the BlackBerry wins There are three considerations that might legitimately lead a company to choose a BlackBerry as its mobile platform, despite all its inferiorities.
One is security. Although Apple provides more iPhone security capabilities than most people realize, it still doesn't have the depth of messaging and device security that the BlackBerry does. Organizations running BlackBerrys can trust that both the data in transit and the data stored on the devices is secure. If a BlackBerry is lost, IT can wipe all of its data and render it useless over the air. You can remote-wipe and incapacitate an iPhone, but only via Exchange. The BlackBerry can have updates and policies pushed to it wirelessly, as well as confirm and log such updates so that you can demonstrate regulatory compliance; by contrast, although the Apple Configuration Utility provides BlackBerry-like security and policy capabilities, you can't force users to install them or even know whether they have done so. And forget about pushing automatic policy updates.
Of course, most organizations don't actually need that level of security, nor do they apply it to other devices such as laptops and employees' home access. But if you follow defense or health-care industry security practices, the iPhone isn't up to snuff yet, not even with third-party add-ons.
Another is use of an e-mail platform other than Exchange 2007. Apple has tied itself closely to Exchange 2007, for user management, information integration, and even security (Exchange is the only way to blank a lost or stolen iPhone, for example). If you use Notes or GroupWise, your iPhones must be managed as Web clients.
The third is the lack of keyboard. All the BlackBerry users I know love their physical QWERTY keyboard. Yes, the touch keyboard works just fine for non-touch-typists like me, but different people work well with different UI methods. So Apple should allow the development of a plug-in or Bluetooth keyboard to satisfy that need. It could even make a model that has it built in -- as long as the screen is not shortened to make room (call it the iPhone Tall).
Apple could easily close all three gaps if it chooses. RIM will have a much harder time addressing the BlackBerry's fundamental deficits. Its iPhone-copying attempts so far -- the BlackBerry Storm and App World -- reveal that RIM fundamentally doesn't get it and is well on its way to becoming the Lotus Notes of mobile.
The fourth reason to choose a BlackBerry is because you really don't want employees to use the Web or apps from a mobile device. If that's your agenda, the BlackBerry will ensure you succeed.
Where the iPhone wins For everyone else, the BlackBerry is yesterday's mobile messenger, way past its prime and heading toward retirement. The iPhone is light-years ahead of the BlackBerry on almost every count. RIM should be ashamed.