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.
For a third option, you can look to hydraulic machines, which use pistons to generate resistance. Hydraulic rowers are quiet, and they also tend to be smaller and cheaper than other kinds of rowing machines, but you won’t get the same smooth rowing feel, or the consistency of resistance, that you would get with an air or water rower. What's more, reviewer after reviewer has found them unreliable and high-maintenance.