Both legit. Make sure you read the fine print though. For example some of the newer blackberrys may require the use of the blackberry data plan for 6 months or else they charge you the extra money that you saved originally.
I've been shopping for phones lately too and I've had semi-problems with both of these providers. They make it a pain in the *** if you are on a family plan. I had to talk to this indian guy for about 20 minutes to get my plan to stay exactly the same as it is now... only to find out they were charging me some crazy upgrade fee that they never mention the entire time.
I'm just going to go to an AT&T store and pay their price for the phone and pick it up in person. This plan will be foiled if I can't talk them out of the upgrade fee.