The A4 is FWD and not a hot hatch, thus less of a drivers car than the 330i. If you want to JUST cruise about, get an E Class or a 5 Series. If you want to cruise, have the odd blat about or B road hoon, get the 330 - it is simply a better car than the A4. Bills on both will be similar, particularly if you go to the dealers but you don't spend £10k on a 2nd hand Audi/Merc/BMW to expect the odd bill of £100 at the most.
Whatever you do, don't buy any of the cars listed in a boggo spec - go 6m older/10k more miles if you have to. If you end up with a bog standard A4, selling it on will be a nightmare and you are punishing yourself when you drive it for a bit of plate snobbery or lack of patience.
BMW all the way for me.