i dont think anyone will ever buy an impreza for mpg apart from the diesel maybe, even in a NA 2.0 the petrol makes my wallet cry, but for me it was the AWD and i always wanted a subaru even if it is a baby for now, could have gone for something else with the same power and alot cheaper fuel easily but i imagine we all have our reasons for getting one. but it feels solid, so far completely reliable and the engine grumbles along nicely no matter what i do to it. never once lost any grip either. wouldnt even consider changing.
out of the 2 options i would go wrx without hesitation. hopefully i will be moving onto a wrx or sti in the future, soon as possible. never seen someone look unhappy driving one. just my opinion :)