Deathmatch: Location support
Both the iPhone and the BlackBerry support GPS location, and the iPhone also can triangulate location based on Wi-Fi signals. The iPhone comes with Google Maps, which can find your current destination, provide directions, and otherwise help you navigate. The BlackBerry requires you to download separate apps to do so. As noted earlier, the BlackBerry App World store's top-rated navigation app is a real pain to use: no turn-by-turn directions, great difficulty in navigating the map, and a UI more interested in issuing confirmation dialogs than providing results. Honestly, I can't see using it. Even though I'm a guy, I think I'd break down and ask someone for directions before trying to work with it again.
Alternatively, I could pony up the $10 monthly fee to use AT&T's Voice Navigator, which talks you through your directions and updates the map as you move along. (There is no iPhone equivalent, for those who travel a lot and need a travel guide, though that may change with the iPhone OS 3.0's new support for voice commands.) Frankly, data services cost too much as it is, so paying even more to get Voice Navigator is not acceptable to me.
The iPhone's integration of location is more pervasive than the BlackBerry's, so you see it in many App Store apps, from a "find my car" app to "tell me the nearest train station." A common "find me" icon works across location-aware apps, and the ability to pan and zoom through maps makes it easy to see where you are, follow the recommended directions, and explore alternatives. There's also decent integration between Google Maps and the iPhone's Contacts app, so you can select a friend's name to have his address entered automatically. (Oddly, you can't edit the contact information in Contacts if you access it via Google Maps.)
The BlackBerry also had trouble finding its bearings via GPS in any location-aware app; often it could not get a location at all. And it sometimes took several minutes (yes, minutes -- try that while driving) to get the positions for those times when it could. I can't blame AT&T for this -- the iPhone uses the same network and could situate itself in mere seconds.