Prefer with sound, it just seems easier to fall asleep when there's sound going on, I don't like super-low sound either, prefer something that's more like "heavy rain/thunderstorms" or even blizzard sounds, not a fan of "gentle running water" or that kind of sound.
Though nothing can replace my favorite way to sleep, in the sleeper of a moving 18 wheeler at night. Some of the best sleep I ever had was when I'd go on trips with my grandpa (he hauled cattle across the country, a lot of the times to Kansas), I'd climb into the sleeper at night while he was driving, hearing the sound of the other vehicles on the interstate as they passed by, the motion from the truck, nothing comes close to that for me as far as the best sleep I ever had.