Shared data plans: Who saves you more money, Verizon or AT&T?

AT&T is launching shared data plans in August. Verizon has them now. The premises are similar -- one plan, multiple phones sharing from a bucket of data. (Voice and texts are all unlimited and "free.") You'll have to pay for each phone that's a part of the shared plan, though.

How do they break down? Which one's more likely to save you money? Let's take a look.

Verizon shared data versus AT&T shared data

Now, that's only half the story. Or maybe only a third of it. Verizon and AT&T each add on a monthly fee for each device that's part of the shared plan. Verizon's is pretty simple -- $40 per smartphone, $10 per tablet.

AT&T gets a little more tricky, but the math is straightforward. Per-device fees start at $45 if you've got the 1GB plan, $40 for the 4GB plan, $35 for the 6GB plan, and the fee drops to $30 a device once you hit the 10GB plan. 

So, let's run some numbers for the plans that match up:

• Two smartphones on a 1GB plan: $130 a month on Verizon, $130 on AT&T
• Two smartphones on a 4GB plan: $150 a month on Verizon, $150 on AT&T
• Two smartphones on a 6GB plan: $160 a month on Verizon, $160 on AT&T
• Two smartphones on a 10GB plan: $180 a month on Verizon, $180 on AT&T

Those plans match up between Verizon and AT&T. Precisely.

Shared data cost per gigabyte per month

Let's look at it from a different angle, though. Assuming two smartphones on each plan, what's the monthly price per gigabyte of data?

So there's that, for what it's worth.

So which is better?

It's kind of a wash, insofar as whether AT&T saves you money over Verizon here. Where the two have the same data buckets, you'll be paying the same per month, if you're only using two phones. If you have more than two phones, you'll save a bit on AT&T, so long as you've got at least the 6GB data plan. Three phones on the 10GB plan would cost you $220 a month on Verizon, or $210 on AT&T. So you'd save $120 a year.

And we haven't even mentioned the difference in networks. Verizon is still light years ahead of AT&T on LTE deployment. So there's that to consider, too. And we're not taking fees into account, either. Also, it's worth noting that AT&T's not forcing these plans on anyone. They're completely optional. If you have a grandfathered unlimited data plan now, you don't have to switch to this.

The real trick to saving any money, with these plans, is to make run the numbers yourself versus your current plan, and then use every last kilobyte without going over.