Because on price the low end TT is cheaper than the 2.2 S so its hardly fair to compete with the 3.2 V6, there are higher spec TTs that can do that job, although the low spec TT is also quicker than the V6.
Specification is largely the same but there are a few key differences to the two cars here. The Alfa's 2.2-litre engine is naturally aspirated while the Audi's 2.0-litre engine comes with a turbocharger. That allows the Audi to trounce the Alfa on the 0-62mph dash with its time of 6.6 seconds - some two seconds faster than the Italian. Even with that performance advantage the Audi returns better economy, combined consumption for the four-ringed car 36.7mpg compared to just 30.7mpg with the Alfa. The Audi also demolishes the Brera on CO2 emissions, with 183g/km a significant improvement over the Alfa's 218g/km.
I agree with above but is annoying that Alfa are that bit behind - TT is common as muck, I saw five red ones in one street yesterday without even paying much attention. Not seen any other Breras this week!