If you are satisfied with less performanced A4, then you would not need the high rpm any way. Turbo cars has higher torque and do it at low rpm. My rate for both G37 and A4:
Performance & Handling (stock vs. stock): G37 no doubt
Interier Qualilty: slight edge to A4
Modability: 2.0T engine wins this one
Reliability: A4 is far behind, G37 wins it