Front space is excellent, even for the tallest of folk. For the two rear passengers, things are less appealing. With the hood up, head room is very tight for those above average height, and the lack of leg room and upright seatbacks mean that, for anyone other than kids, the back of a BMW 4 Series Convertible is a more appealing place.
With the roof up, the C-Class Cabriolet has a bigger boot than that in a 4 Series Convertible, with enough space for a couple of mid-sized suitcases. You can also drop the rear seatbacks to gain extra length, although the shallow boot opening prevents you from getting bulky items inside. If you retract the roof, it severely restricts the boot’s height and robs it of space, immediately rendering it far less practical.