When I purchased my soot chucker back in 2005, it was an ex dealer demo car and thus pretty much fully loaded. They wanted £1800 more than a similar petrol model (albeit with poorer spec) and £3K less than then cheapest MK5 GTi they had (although to be fair the GTI hadn't been out long).
I knocked them down and eventally got it for only £350 more than the petrol model (thus £4.5k cheaper than a GTI). Whilst I would be the first to agree with most of what everyone has said about a petrol being a "nicer" drivers car for spirited driving, TBH, round my way a t least, rush hour traffic is so dense, that 0-60 times actually mean nothing. The beauty of the derv is that it just pulls and pulls in any gear, meaning it's a much more relaxed drive than revving the nuts off a petrol just to be first to the traffic lights.
Also over the last nearly 5 years of ownership, it' snever dipped below about 47mpg, whilst regularly seeing mid fifties. So my extra £350 over a petrol was deffo money well spent.
As with everying thing, there will always be plusses and minuses with any car, but I really believe whether you choose a GTI, a Derv or a Lesser Petrol engined model, the MK5 platform was so good, that you are pretty much guaranteed a decent ride.
Now if motoring costs were not a factor (aka I win the lottery), then yes, I would probably be driving a GTI or better still an R32 or New Golf R, or Aston Martin or Ferrari or..........