Average quality. When in pulse mode or high power becomes noisy, noise comes from how speed is regulated and is common to both models I owned. Efficiency decreases over short time, need cleaning regularly. Tiresome to adjust waves and synchronize multiple units over wi-fi. No backup settings after power out. Photodiode of poor quality, and you can't use one diode for all controllers, so you have to place all your controllers in a lightbeam for nightmode to work.
I have the RW-4 in my tank, and it provides great flow. I run the W1 program (short pulse with the dial on the 8th line) - this gives me a decent wave, and my frogspawn loves the sway!
More wave setting options than you could ever need. Pretty quiet.
Not too bad for what you pay.
Have 4 in my tank, never failed. Low noise.
for the price can't complain