I really doubt a machine pistol and a revolver are going to heavily shift the battle in favor of the pre-order guys. Personally I only pre-ordered the spec-ops pack because the Hockler looks nice.
But to sell a game with this sense of "fair and balanced, everybody has a chance" and then only give certain items to certain people who preordered from a certain place is, even if only a slight one, a hypocritical behavior.
It's not like they're saying "you get an extra gun for preordering", it's "you get an extra gun for preordering from these two places", if you preorder elsewhere you either get some extra skins or nothing.
If all the guns have different stats to make them more useful in certain situations then your giving some advantage to the guys that have them in those situations.
Same applies if the Greeneye scope or soda can silencers have stats different from the scopes/silencers in the game, which further compounds the advantage that someone who pre-orders from walmart/amazon will have.
I don't particularly care about the stuff, but handing out "stat" items as pre-orders in any MP game gives those that pre-order an advantage.