One of the reasons he's lucky to get on the end of one or two crosses in a game is that he can't get above defenders to head the ball. That goal against Arsenal is the last minute, Arsenal's defence is completely stretched and he's in a race with Mertesacker to get to the ball first, good header like but that situation won't come up very often. Andy Carroll is different because he has a massive leap and is also a bit taller so you can put in any kind of cross and Carroll will probably get on the end of it