I have said, and I'll gladly say it again, that I much prefer the brand of football a team is capable of playing with a player with Welbeck's traits as opposed to a player with Giroud's traits. I have also previously said that Giroud is quite obviously in much better form than Welbeck is at the moment. Ev has it right in the sense that Welbeck has regressed compared to when he first got here.
However, my biggest concern right now regarding the CF position is that Giroud AND Welbeck are on the pitch at the same time quite a lot. Personally, I don't particularly agree with that, because I think Welbeck should mainly play as a striker in order to improve to be really useful for us. IMO he doesn't really have a future here as a wide player. At least not the way we play right now. In the form both Giroud and Welbeck are in right now, I'd have Giroud starting at CF in 2/3 games, and Welbeck in 1/3 games. It would help keep Giroud fresh, which to me is vital for him to be useful, and it would give Welbeck game time at CF to hone his skills in that position. If form shifts - then swing the ratio of games.