Hmm, no, you're wrong. Barcelona is the only team who play the 4-3-3. United, Liverpool and Chelsea actually play the 4-2-3-1.
Anyway, I don't see the point of having two strikers when you can have more players involved in the game. For example, Trezeguet. He doesn't do anything and is never involved in the game, its like playing with 10 men with him on the field. Instead, you can put a player like Giovinco or another creative AM/winger on the field and he would definitely create some chances for the team.