An Apple (NASDAQ:AAPL) iPad becomes infinitely more useful when paired with data plan, but picking the right one can be a challenge. Make the wrong choice and you're left with choosing between not using your tablet until the next billing period or paying what can be hefty overage charges.

All four major wireless carriers AT&T (NYSE:T), Verizon (NYSE:VZ), Sprint (NYSE:S), and T-Mobile (NASDAQ:TMUS) sell the iPad and all do so with differing plans and methods of selling you the device. While the full retail price for iPad is set by Apple and generally does not vary between the carriers for the most recent devices, varying data plans and financing offers make overall pricing a bit of a moving target. 

That makes it difficult to know when you're getting for what you're paying, and what the potential hidden fees and overage charges are. And while there are a variety of iPad models being sold, including the Mini, for the purpose of the comparison we're going to look at the most up-to-date iPad: the Air 2 in the 16GB model.  We're also assuming that you're a new customer looking for an iPad alone, not bundling the tablet with phone service.

The Apple iPad Air 2 Source: Apple 

AT&T offers iPad 2 Air in three different ways: a two-year contract, a 20-month financing plan, and buying it outright for $629.99, the last of which does not require a service plan contract. The installment plan requires a monthly payment of $31.50 for 20 months or $630. The installment plan, like buying the device outright, does not require a contract, but you do have to make all the remaining payments if you elect to leave before the 20 months have passed. The contract offer requires a two-year commitment and anyone electing that option gets a $100 discount, but must pay $529.99 upfront.

The interesting thing is that unlike its phone plans where customers get better monthly prices if they finance or buy their devices outright, AT&T charges the same data rates no matter how you acquire your iPad. The company currently offers three plans:

250MB Plan3GB5GB
$14.99 (overages $14.99 per 250MB) $30 (overages $10 per 1GB) $50 (overages $10 per     1GB)

That's a peculiar pricing model because there is no reason to sign up for the 5GB plan. If you get the 3GB plan and use 5GB, the price with overages will be the same as if you had committed to the more expensive option.

When it comes to buying your iPad Air 2, Verizon offers a similar set of choices to AT&T. A two-year contract gets you $100 off the $629.99 retail price or you can buy it outright. The only slight variance is that the company offers a 24-month financing plan where purchasers pay $26.24 a month ($629.76 in total) to own the tablet.

For data, Verizon adds a $10 monthly "line activation fee" for each device. Data prices are the same for financed, purchased, and contracted tablets.

Customers can pick from data plans ranging from 2GB all way to the $710 100GB plan. Verizon allows data plans to be shared by as many as 10 devices, but we're just looking at one here, so let's cap out our comparison at 10GB because it would be hard to use more than that on a single device.

Data 2GB 4GB 6GB 8GB 10GB
Cost $20 $30 $40 $50 $60
Total: $30 $40 $50 $60 $70

*Total includes the monthly line charge

Verizon charges a flat $10 per 1GB of date should you go over your allotment.

Sprint offers a variety of choices with a leasing option on top of the traditional purchase, finance, and contract options. The lease is the cheapest way to obtain an iPad Air 2. Customers who choose that option pay $20 a month, but do not own the tablet. At the end of 24 months, the customer can either keep paying $20 a month or return the device. The installment plan is similar to Verizon's with 23 payments of $26.25 for 23 payments and a 24th of $26.24 (totaling $629.99). The two-year contract deal is the same $100 off that Verizon and AT&T offer.

Sprint charges the same prices for data no matter which method you use to acquire your tablet.

Data 100MB 1GB 3GB 6GB 12GB 30GB 
Cost $10 $15 $35 $50 $80 $110

*All overages are $0.015 a minute

T-Mobile no longer offers contracts of any type, so your only choices are buying the iPad Air 2 outright for $629.99 or financing it over for $26.24 for 24 months ($629.76 in total). Data plans, which are the same for either option, are all unlimited data, but customers pay for a certain amount of data at 4G speeds. 

Data 1GB 3GB 5GB 7GB 9GB 11GB
Cost $20 $30 $40 $50 $60 $70

Which plan is the best?
Since there is essentially no difference between the purchase and finance deals offered by the various carriers, the only differences come with Sprint's lease option and the various data plans. The Sprint lease is the cheapest way to have an iPad, but paying $480 over two years is a lot to spend to not own a tablet -- especially when resale value would almost certainly be more than the roughly $150 saved over the full purchase price.

As for data, it really depends upon how much you plan to use and what you're willing to risk in overages. AT&T offers the cheapest plan, but you get very little for the money. T-Mobile prices get better as your buy more data and the lack of overage charges in general make that carrier worth a look.