Welbeck creates chances for himself too, which is something that Giroud very rarely does. For instance, it has to be just a matter of time until Welbeck scores one of them curlers in the far corner. He has tried a few times, and he is very confident in that move. What he lacks a bit IMO is to be a bit more selfish once he gets the ball in the box. He still takes the ball out of the box too much, or looks for a pass. However, he has a much quicker shot movement than Giroud, so although Giroud looks to finish more often in those situations, his attempts are mostly blocked. I'd say Giroud uses his body better when getting high balls played to him, he is better at winning the physical battles when crosses/corners are played in, and he is a more reliable link player. Personally, I have no doubt that Welbeck will learn to use his physique better, and that he will look to pull the trigger more often when getting the ball in and around the box. Once he develops with that, then he will be markedly better than Giroud. At the moment there isn't too much between them, although I much prefer Welbeck's game.