The battle between the Audi A4, the BMW 3 Series and the Mercedes-Benz C-Class is one of the most tightly fought anywhere in motoring. The margins are super-slim in pretty much every area, and none more so than in this one. They’ll all cost you around the same to buy, they’ll all protect your investment pretty well with very similar resale values, and with very similar figures across the board for CO2 emissions, fuel economy insurance groupings and maintenance, they’ll all cost you a very similar amount in day-to-day running costs. As a result, you shouldn’t look to the figures to make your buying decision for you, but on the plus side, it’s nice to know that whichever you decide to plump for, you won’t be losing out to any great degree.