But for comparison's sake, let's assume you're an individual, moderate iPhone user who talks 450 minutes a month, uses somewhere up to 2GB of data, and sends at least 100 text messages--around three a day--every month. Sprint, despite the initial sticker shock of its voice plan, would actually be the cheapest option here at $80 a month. AT&T would come in a close second at $85 a month, and Verizon would rank third at $90 a month.

Then again, maybe you talk more, text less, or have more phones floating around your household. In those cases, the dollar metrics will certainly change. What's more, you might be willing to pay more for a carrier that provides a stronger signal in your neighborhood than for one that constantly drops calls. Now that competition has arrived, iPhone users are going to have to do a little more homework.