Depends on what you plan on using your phone for...
iPhone is more of a entertainment device rather than a "business" device, like the BlackBerry. If your work place supports BES, I would say get a BlackBerry. If you dont even know what BES is, then just get an iPhone.
If you are such a regular joe, that doesnt need your email Pushed either, then its more of a reason to get an iPhone.
On a side note, BB8800 isnt a fair comparison with the iPhone. BB8800 is more of a business class phone rather than a consumer. Although all blackberries are more "business" phones, the Curve is a fairer comparison. It lacks the GPS but it makes up with a 3.5mm headphone jack and a decent camera.