advantages of manual:
•more hp gets to the rear wheels (power is always lost to the driveline, so not all 280 hp get to the wheels, manuals usually lose 5-10%, and autos 10-15%)
•less weight
•more gear ratios
•can play with the clutch for better lanuch
(above = faster, and better fuel economy)
•better reliability (auto's usually break every 100-150 000 km, manuals need new clutches but hardly ever break)
advantages of auto:
-easier (you end up going faster unless you're experienced)
-traffic
personally:
I'd get the a5 in this car if I could aford one (I wish). It's not a pure sports car, it's a luxury sports car, and if I bought a manual I think I'd miss the auto more than I'd miss a manual buying an auto. You can pick which gear you want with the auto, and you can let it do it for you if you want. But I would want the sports package on the auto to get the 18" wheels and suspension from the manual...