I think the A6 is more of a fair comparison to the 5-Series as the A4 is more 3-Series size isn't it? Not bad size wise, just not the biggest in the rear i found... I do prefer the drive of the BMW's though, the Audi's are just a bit bland in my experience... they're good at what they do but just left me a bit flat i thought, i nearly bought an A4 2.7TDi Avant that we had here so it was a choice between that and the 5-series but the 5-series just suited me better.
The Avant was good but equally you don't store stuff up that high anyway and probably don't want stuff out on show so for me there was no real benefit in going for an Estate... the boot on the 5-Series is huuuuuuge, i can get all my detailing gear including a pressure washer in there and trust me that's a LOT of stuff, far more then i used to take racing haha.
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