Oh, if I had a quid for every time i'd heard this one.............
IMHO, the TDI.
Less overall BHP but the peak power comes in earlier than the FSi and clearly is much tourquier. Cabin noise is slightly higher in the oil burner but only really noticable on tickover. 30-40% better fuel consumption and only a few hundred pounds more to buy. Yes the fuel is more expensive by a couple of pennies but obviously you'll be filling it up less often.
Residual values are higher on diesel models but only really by the amount they cost you more to start with.
The FSI is a much more revvy engine than the diesel but some people like that.
If it helps, as a guide, we sell 7 GT TDIs for every GT FSI. Yes, 7 to 1.

VWmd