On the surface, T-Mobile's new plans sound like a significant discount over the competition — the carrier now offers unlimited talk, text, and data for only $70 per month ($120 per month if you're a couple of two, or $150 per month for a family of four). However, once you start to pull apart the new plan, it's not quite the dramatic difference it seems at first glance. Let's dig into T-Mobile's new offerings and see what the best option is for buying an iPhone 5 now that the nation's fourth-largest carrier is finally offering Apple's flagship handset. For the purpose of this comparison, we'll be looking at the costs for individuals, as well as two-person and four-person family plans. We also ignored the standard activation fees, as carriers pretty frequently remove them during promotions.

Verizon

The nation's largest carrier did away with unlimited data and moved to its new "Share Everything" plans last year, which get you unlimited voice, text, and a pool of data between devices. For an individual buying a single iPhone 5, you'll pay $100 per month for 2GB of data. Over the course of two years, you'll pay $2,599.99 for service and the device.

Under our two-person family plan, shoppers can get 4GB of shared data for $150 per month, while a family of four would get the same 4GB of data for $230 per month ($240 gets you 6GB, while $250 steps up to 8GB). That's $3,600 for the life of the contract for our two-person family, plus the initial $399.98 outlay for two 16GB iPhone 5 devices, making it $3,999.98 for the life of the contract (not including any taxes or fees). The family of four would pay $5,520 plus $799.96 for four iPhone 5s for a grand total of $6,319.96 for two years of service.

AT&T

AT&T's plans are nearly identical to Verizon, though its Mobile Share plans are a bit more friendly to larger families when compared with Verizon's offering. For individuals, AT&T offers 4GB of data and unlimited talk and text for $110 per month. A full two years of service plus an iPhone 5 would cost a total of $2,839.99.

A two-person family can get 4GB of shared data for the same $150 per month, with the identical unlimited voice and text offerings. That would give a couple an identical $3,999.98 two-year price for service plus two iPhone 5s. And while the four-person family would also pay $230 per month, that nets 6GB of data instead of four — much more suited to a larger group. $240 per month steps the data offering up to 10GB per month, more than double what Verizon offers for just $10 more per month. An AT&T family of four would pay the same total of $6,319.96 for two years of service, four iPhone 5s, and 6GB of data per month.

Sprint

While Sprint used to be fairly affordable, the company still places a premium on unlimited voice — and as such, its plans are almost prohibitively expensive when you consider the downsides to using the carrier (a limited LTE rollout and extremely slow 3G service chief among them). Individuals don't make out too badly — Sprint's $109.99 plan offers unlimited voice, texts, and data. Over the course of two years, it would cost $2,839.75 for service and an iPhone 5.

Things change a bit when you add multiple lines, however. A two person family would pay $209.98 per month for unlimited voice, texts and data (the big advantage Sprint does have over Verizon and AT&T). While a $60 monthly surcharge for unlimited data might be worth it for some, things really become untenable when looking at plans for a four-person family — unlimited voice, data, and texts would cost a whopping $409.96 per month, significantly more than Verizon and AT&T's plans.

Over the life of the contract, a two-person family on Sprint would pay $5,439.50 for service and two iPhone 5s, while the family of four would pay an insane $10,639 for service plus four iPhone 5s — that's a heck of a premium for unlimited data. Sprint does offer options to step down your minutes, which we'd recommend most users investigate — the carrier includes unlimited calling to mobile phones in its plans.

T-Mobile

Here's where things get interesting — if you were expecting T-Mobile, the "Uncarrier," to ride in on its white horse and save the day, it's not quite so simple. On the surface, T-Mobile's plans look cheap indeed, but the recurring monthly phone cost changes the math a bit. For an individual, T-Mobile's unlimited voice, text, and data plan comes in at $70 per month, but you'll also need to add a $20 device charge every month as well, for a total of $90 per month. Over two years, that'll run you $2,259.99 for service and an iPhone 5.

For a two-line plan with unlimited data, T-Mobile only charges $120 per month. However, unless you pay the full, unlocked cost of your phone up front, T-Mobile will also charge another $20 per month, per line (that's for the iPhone 5 and most other newer phones, that monthly charge does vary). For this two-person family, unlimited voice, data, and texts costs $160 per month — comparable to AT&T and Verizon's pricing, though you're only paying half as much for the phones. Over the course of two years, that works out to $4,039.98 for unlimited data and two iPhone 5s. Four lines on T-Mobile with unlimited comes in at $260 per month. Over two years, unlimited data plus four iPhone 5s comes in at $6,639.96.

The breakdown

Verizon AT&T Sprint T-Mobile Individual $2,599.99 $2,839.99 $2,839.75 $2,259.99 Two people $3,999.98 $3,999.98 $5,439.50 $4,039.99 Family of four $6,139.96 $6319.96 $10,639.00 $6,639.96 Caveats Verizon: 2GB data for individual, 4GB for 2 and 4 person plans. Includes hotspot.

AT&T: 4GB of data for individual and 2 person, 6GB of data for 4 person. Includes hotspot.

Sprint: Unlimited data, does not include hotspot. Add 2GB hotspot for $19.99 / month or 6GB for $49.99 / month.

T-Mobile: Unlimited data, includes 500mb of hotspot. Add 2GB hotspot for $10 / month or 4GB for $20 / month.

Wrap-up

While there's no denying that T-Mobile's new plans are the cheapest around, it's not the slam-dunk the carrier would have you believe. For a couple of two, it's about $4,000 for shared data on Verizon and AT&T, or the same price with unlimited data on T-Mobile. You'll just have to decide what matters to you more — both Verizon and AT&T have much larger LTE networks right now, but you're stuck in a two-year deal with no real affordable upgrade options, while T-Mobile offers you the promise of being able to escape if you need to or try another phone if you want to. Of course, you'll need to pay up before you do so — T-Mobile customers have to make up the difference between what they've paid so far and their old phone's retail value if they want to try a new device.