I think it's mentality/personality. He seems brutally passive/timid at times.
Yeah, I think for Mhki it's probably that (it's actually that reason I wasn't hugely keen on his signing in the first place), I just don't think he's the sort of person who will take the game by the scruff of the neck and singly handedly control it.
That's a bad thing, but with the right players around him it needn't matter too much. If we can get in a position where someone else is the primary playmaker and Mhki is responsible for flittering around providing little pieces of quality like that goal I think that would work quite nicely.
If you look at the season as a whole I think Lingard has been better. Mkhitaryan's best form has been in Europe against weak sides. In the PL he is virtually ineffective against sides that sit in. I actually think he would have been better last week if he had started against Everton as they played a bit and gave us some space.
I think he's got more ability but doesn't have the personality to go with it. I don't know if I agree Lingard's had a better season, but it's close, and the fact it is close is a pretty damning indictment on Mhkitaryan.