IME working for another cell phone company, and being a Verizon customer, you are better off going directly through Verizon. The actual monthly cost will be the same, and the cost of the phone will not be that different when you look at the possible ramifications. When you purchase through another vendor, you are purchasing through a third party company (another hand in the pot). Many times their deals are tied to additional requirements- like you will get an additional discount on the phone, but you have to keep a data plan that you do not want or need. If you fail to keep the plan, they can charge you additional costs.
The most important thing is carefully reading over anything you sign, asking about any catches for the deal you are getting, watching your next couple (first couple) of bills very carefully, and remembering that if it sounds too good to be true, it probably is.