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I use both. The Bold is supplied by work. iPhone still wins hands down. Only thing the Bold has on the iPhone is a slightly better battery.
 
I went from the Bold to the iPhone 3G 2 months ago and the difference in battery life was significant.

But I'm getting about the same battery life with the iPhone 4 that I was getting with my BB9700, so I'm very happy with the switch.
 
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