Mercedes-Benz E400 Cabriolet 4Matic AMG Line 2018

It's not hard to understand why. Roof down you're going to that much more exposed to its charms – or otherwise – and because such cars champion laid-back luxury you really should have a powerplant of commensurate depth and refinement. Unless you're talking about a carbon-tubbed supercar, convertibles are also heavier than their coupe counterparts, so going with a punchier powerplant is of practical benefit, too.