Michu had scored 15 La liga goals last season.
Gervinho and Giroud were great in ligue 1 and here they are average.
Grenier is 22 and hasn't done anything of note.
He could turn out great but chances are he isn't going to be good enough and he clearly is not a finished product.
At 22 I'd take James Mccarthy though not another ligue 1 kid who'll be average or leaves in 2 years if he's any good.