My quick bottom line impression is that both plans are similarly priced. Both plans include unlimited minutes / unlimited texting and shared data.
The ATT plan is a bit more confusing since the price per phone varies depending on the amount of shared data chosen. Also, ATT decided to go right from 1GB to 4GB, skipping 2GB altogether, as well as jumping to higher increments in the 10+ range. Verizon goes from 1GB to 2GB and then adds 2GB at each step up, providing more options.
Check out the chart below, courtesy of Droid Life. You'll see that Verizon charges a flat rate of $40 per phone for each smartphone and the price only goes up as the shared data increases. The ATT plan starts out at $45 per smartphone and the price per phone goes down as your data rate/price goes up. So you'll need to truly plug in the numbers to compare prices between the carriers.
As an example, if you went with 2 smartphones and 1GB of shared data, ATT would be $45x2 + $40=$130 and Verizon would be $40x2 + $50=$130.
If you had two smart phones and went with 4GB of shared date, then it would be $40x2 for the smartphones on both plans and then $70 for 4GB of shared data for a total of $150 plus taxes with either carrier.
So you can see, even with the different pricing models, the cost is the same at least at the 1GB and 4GB levels. Things vary slightly at other data points.
The bottom line is that, as expected, both plans are pretty comparable. ATT has had over a month to take a look at what Verizon is offering and of course wouldn't want to put out plan offerings that differ all too much from their main competitor.
There is no real reason to switch carriers based on differences in their shared data plans, unless perhaps you REALLY wanted to go with a 2GB shared plan on ATT and didn't want to pay a little extra to have 4GB instead, since 2GB isn't currently offered.
Of course you do NOT have to switch to a shared data plan with either carrier. If you are a heavy user of minutes and text, the shared data plans probably make good sense.
For our two smartphone plan, we predominantly utilize data and hardly ever use minutes or out of network texts, so it would be about a $15 increase to convert over to shared data. For that reason we will remain with a traditional plan. Check out the numbers for yourself and see what you find.
Are you thinking about converting over to a shared plan? Are you finding that you may end up saving $ doing so or are the unlimited talk/texts more a driving factor? Let me know your thoughts!