Water machines are generally quieter than air rowers - you can still hear the water moving in the tank, but users tend to find this a pleasant ambient noise. Water rowers also tend to require little maintenance. Because there's a tank full of water involved, however, these can be very heavy, and larger than most other rowers: if you have a smaller home, a less-than-permanent workout space, or you move frequently, these might not be best for you. And because they're so high-performing, they do come at a high cost.
One downside of the Waterrower for me are the footrests. Whilst they are perfectly adequate if you want to row in shoes, rowing barefoot, which is something I like to do, is impossible. The plastic is completely square at the bottom and has sharp edges that cut into your heels. I also found that my shoes get caught when trying to put them in and out of the holders, which is a bit irritating.
Outside of resistance type, we found the number-one arbiter of ride feel to be cord quality. Water ergometers tend to employ nylon cords, while air ergometers feature metal chains — a durability factor we anticipated would result in our favoring air. But while all three water rowers aced our expectation of smooth, high-tension strokes, perfecting the chain seems to be more difficult: Some tug with just a slight rumble, others feature bouncy, grinding chains that are incredibly loud, something akin to angry snoring. As for nylon, the best wind and unwind like elastic silk — no slack, no sound, no catching, just perfectly even tension throughout the stroke.