It is not a knockoff at all. Smith and Wesson has been around for much longer than Glock.
If it is the S&W MP it is a "knock off" but a really good one!!! It was more comfortable than the glock and basically just as easy to clean, etc. It was a bit nicer feel too! Either one is good if you like the way they feel. I'd try the Baretta and Sig Saur as well!!!