What are going to be the drawbacks of having a thunderbolt muffler as opposed to a flowmaster?

im going in on friday to get a cat-back dual exhaust put on my 01 dodge ram. i originally wanted a flowmaster, but the mechanic was trying to talk me into getting a thunderbolt. he said that flowmasters patent ran out and thunderbolt was an exact copy, just cheaper.|||thunder bolt wont last as long as flow masters will and he is right they are a little cheaper,but they are also cheaper made,remember this when you put them on,here's a site that might have what you want for it,good luck.http://www.autopartswarehouse.com/ PS you,ll have to type that in yahoo isn't posting sites tonight ,they messed up again,good luck.