I think it depends on your style of play. Are you going for a big strong header to outmuscle everyone around him, taking advantage of good crosses to the box (Drogba)? Or the same strong fella used as a 'flick-on' station for your mids (Zigic)? Or perhaps you need that speedy guy who moves into position behind enemy lines for the clever through ball (Eto'o)?. Or what about the intelligent forward who is used in a controlled build-up, interchanging passes with wingers/MC's (Henry)?
And so on, and so on...
Need a bit more info...