Do you lose more calories on a rower than an Exercycle?

Depends on which machine gets your heart rate up the most, and how long you can keep going.

Calorie burn is pretty much all about getting your heart rate up and keeping it up for an extended time. Most people would burn more calories on something cycle-like than a rower, as the rower is more likely to tire them out too soon to achieve an worthwhile calorie burn.