Currently, I'm using a sim with a blackberry data plan from at&t in an unlocked iPhone. Will switching to an iPhone data plan give me better service? I've noticed that I was getting better signal strength with the blackberry than with the iPhone. Plus, data speeds seemed better with the blackberry. I borrowed another blackberry sim from work and tried them side by side - the blackberry seemed to perform better in terms of signal strength and data speeds.

I really don't care about visual voicemail. I just want the best possible service.

AT&T supports 2 forms of data. 3G, and Edge. 3G is much faster. The Iphone only supports Edge. So it's possible the blackberry supports 3G, and so is much faster. Putting the blackberry sim in the iphone shouldn't increase data speed.

I would check the cost difference between the 2 plans. AT&T normally has very expensive data plans. The iphone has a cheaper data plan.

Also you mentioned that the blackberry sim worked better in the iphone than the regular sim, or are you comparing blackberrys to apples? I think the blackberry will always win with data speed if it's 3g. (insert fruit jokes here).

The blackberry has an EDGE radio, not 3G. I'd prefer to stick with the blackberry plan because my company will reimburse me for it, but not for the iPhone plan. However, I'd get an iPhone plan if it meant better service / faster browsing.