It's time to rollover. Not your dog \u2014\u00a0your monthly wireless data, at least if you're a T-Mobile or AT&T customer. The two carriers launched dueling rollover plans \u2014\u00a0T-Mobile last month, and AT&T this week\u00a0\u2014 proving once again that competition in the wireless market is for real, and it's a real benefit for consumers.\nThe obvious question, of course: Which plan is better? Both of them certainly have their good points, but they're both also limited in a number of important ways.\u00a0\nT-Mobile's program is called Data Stash. It lets customers carry over unused monthly mobile data into the following months. The data stays in your stash for one year and then goes away. New and existing customers get an initial 10GB of free data for the "stash" to kick things off, and that bonus data lasts through 2015.\nHowever, there's a big catch. You can't use Data Stash unless you pay for at least 3GB of data per month, which is quite a bit.\nEstimates on how much data the average consumer uses vary widely, but what's important is how much you use. If you've owned a smartphone for a while, you probably have a pretty good idea of your monthly data use. If you don't, go check your previous bills.\nT-Mobile's plan also has another limitation: It\u2019s only for individual plan holders. So if you're hoping a group of people \u2014 whether it's your family or your coworkers\u2014 will be able to take advantage of Data Stash, you're out of luck. Given the relatively high data limit built into Data Stash, that's a significant drawback, and it does seem to indicate that T-Mobile isn't interested in meeting the needs of businesses, at least not yet.\nAT&T's new plan, which goes into effect on Jan. 25, is the same in theory \u2014 you rollover your unused data \u2014 but it differs from T-Mobile's in a number of important ways.\u00a0First of all, there's no minimum amount of data you must pay for; no matter how much data your plan includes, it can be rolled over. If you're on AT&T's Mobile Share plan, all of the data used by the group can be rolled over. However, there is a catch, and it's a big one. Your unused data is only good for a single billing cycle, which is roughly a month. After that, you're back to square one.\nDespite the limitations, both rollover plans are good for consumers, and in AT&T's case, they're good for small businesses or work groups. T-Mobile's outspoken CEO, John Legere, crowed that AT&T introduced its rollover plan as a response to T-Mobile's earlier move. AT&T denied the charge and said it had already planned to make the announcement at this week's Consumer Electronics Show (CES) in Las Vegas.\nFrankly, it doesn't really matter who was first. A good idea is a good idea, and competition is forcing all of the carriers to offer better deals. More interesting, though, will be the response of the other two major carriers: \u00a0Verizon and Sprint. I bet one or both of them follows suit in the not-too-distant future.