There are two cars to which the 500c could be aptly compared; the Mini Cooper Convertible and the Smart ForTwo Cabriolet. So here's the basic rundown.
The Smart ForTwo is considerably cheaper, but it has no back seats at all and it doesn't drive nearly as well as the 500. You get what you pay for.
The Mini Cooper is considerably more expensive than the 500, but it's also more fun to drive with more engine power, crisper steering and firmer suspension. On the downside, the Mini uses more gas and, even though it's a slightly larger car, the Mini feels more cramped inside. Hopping out of the 500c after two hours of driving with the top up, I felt just dandy. Two hours in a Mini would have me reaching for a bottle of aspirin.