m3 & 159
we've got a 159 sw 1750 as the family wagon, also used to have an e46 m3. so understand your question.
used to move between the two quite happily, never felt sad about driving the alfa instead, indeed much preferred the interior and quieter ride when in the mood. sure the engine doesn't make much noise, but you'll not miss the performance 99% of the time.
in fact i'd say that motorway speeds, say 50-80 in 6th with the turbo is singing its just as fast as the m3 in 6th. [ change down 3 ratio's and it's not the same story...] but real world its properly nice to drive.
turbo lag definitely exists <1500rpm which takes some getting used to pulling away, but beyond that its non existent. fuel economy. popular subject here, would you believe i'd say they are about the same, but longer range on the 1750 due to bigger tank so no savings there.
tyres cost about the same and seem to last as long, tracking helps a bit allegedly.