Air rowing machines offer a more realistic rowing experience and are excellent for building strength. Magnetic rowing machines make no noise at all and can be used to get a good overall workout. Air rowing machines do, however, burn more calories per hour.
Air rowing machines use a flywheel to generate air resistance. The overall degree of resistance on an air rowing machine can be adjusted, but in general, the harder and faster the user rows an air-rower, the more intense the workout becomes.
Magnetic rowers use a magnet to generate resistance. The resistance level can be adjusted, and it does not increase in response to the user trying to row harder or faster.