Interior build quality and comfort have typically been a bit better in the C Class sedans than they have in other smaller sport sedans. And the latest models remain faithful to this impression, as one of the best choices for long-distance touring among vehicles this size.
You'll have no problem getting comfortable in the C Class's front seats; they're among the best in this class, with enough support and comfort for both long hauls or somewhat spirited driving. The driving position is at a good height, and highly adjustable for different body types, thanks to a tilt/telescoping steering wheel, power seat adjustments, and the tall, glassy cabin easing visibility.
Just don't plan on having adults ride in back, even across town, until you check out the space back there. With legroom at a premium, if you plan to scoot the front seats near the back of their travel, there's almost no rear legroom left.
Trunk space is on the smaller end, at 12.4 cubic feet in sedans and 11.7 cubic feet in the coupes, but it feels about right given the size of the rest of the vehicle. You'll have no problem fitting a couple of airline carry-ons back there.
Opting for the C63 AMG will provide seats with just as much comfort, but much more aggressive bolsters that fit more snugly.
Seating aside, interior appointments are fully to snuff for the American market, with an array of cupholders, cubbies, and door pockets, plus a roomy console and large glove box. And while we haven't put C Class interior materials in the top tier in the past, the current version impresses with mostly luxury-grade plastics; nice leather; and wood, metal, and other special trims.
Throughout most of the lineup, the cabin has a quiet, refined feel that's above and beyond most models in this class. Road thrum over coarse surfaces--a weak point for many sportier small sedans--is really minimal here.