With magnetic rowing machines, adjusting the resistance means varying the distance between a flywheel and one or more strong magnets. This is done either manually, using mechanical sliders, or digitally by the console controls. Like hydraulic rowers, magnetic rowing machines operate quietly and have a compact design for easy storage. Unlike hydraulic rowers, they can provide a smooth and consistent workout. It's a very different kind of feel to what you'd expect from an air or water rower, though. You still get a good workout, but it doesn't simulate the sensation of rowing in quite the same way.
Do you want pre-set workouts? Are you one of those people who can't go for a run without an app, a training plan, and a corresponding diet worksheet? Even if you don't take it that far, pre-programmed workout routines can really enhance your rowing machine experience by varying your workouts and guaranteeing you a challenging session. If you're trying to decide between two machines, you could do worse than to choose one with a good range of built-in workouts.
The rowing machine itself is unlike any other on the market with its patented water filled flywheel. It is hard to exactly copy the action of a scull on the water, but the mechanics of the flywheel spinning in water comes in a close second on dry land. The fact that the water is 800 times denser than air means that there is no need for any extra resistance or dampening that you will find in normal air rowers. The faster you pull, the more resistance is generated giving it infinite variability. However, if you want to be able to practice rowing with a faster stroke, you will have to reduce the amount of water in the tank unlike an air rower where you just have to adjust the baffle.