I went the other way - MK4 Mondeo Titanium X TDCi (140) to Mazda 6 2.2 Sport. My insurance is about £40 more for the year, but tax is about £35 less, so it works out pretty even. Servicing / parts will be more expensive for the Mazda, but I really do think that the Mazda is the nicer car, so I'm prepared to spend the extra.