I had a 2004 A4 1.9tdi quattro sport and bought a 2005 BMW 320d sport. The audi is not very smooth going up through the gears at all, very jumpy (something to do with torque!) but the bmw is very smooth accelerating. The BMW is much smoother on Irish roads aswell. In terms of build quality, I would defo go for the audi, its just got a better finish inside in terms of buttons, dash, extra's etc. For example, the BMW has no cup holder!! In my opinion the BMW sport looks much better than the Audi sport. All in all, its hard to say! if I was doing it again I'd probably punt for the BMW, its more expensive but better engine and smoother ride.