Technically this is true but it only ends up being a couple dollars difference once tax is figured in plus you don't get that $20 bonus until a month after you pickup the game. I'll take the money off the top even if I might have to wait a day or two to receive the order.
I'm in CA, so newegg would charge me tax too. If you are not in CA however, and your tax rate is M, as long as M<13.33% the BBY deal is better. Of course unless you have little use for BBY GCs, which would be absurd.