I'm no expert, but here are my thoughts based on my limited personal experience. A few months back I bought two Menaces and a coupler to make a full Maul staff. For months I had planned on only ordering sound in one of the two hilts but changed my mind and got sound in both, mainly for the two distinct power up and power down sounds when slightly staggering those actions.
When I assembled the staff and tried the limited motions I can manage in my house, I discovered another unexpected benefit. Since the sound boards (and their motion sensors) are located near the pommels of the hilts, the resulting placement near the center of the staff naturally reduces the relative movement of the boards during some moves which means the detection threshold for a swing noise may not be reached. With two sound boards in slightly different locations, the chances for swing detection go back up somewhat since it's unlikely both will follow identical paths. You can change the detection threshold in the launcher of course, but it's a balancing act to avoid making it too sensitive. Also, regarding both boards triggering different swing sounds, the staff is just two lightsabers stuck pommel to pommel so why wouldn't the two component sabers make different swing sounds?
As others have stated, I highly recommend going with V4 sound whether you get it in one or both hilts. That additional $10 gets you a bunch of extra functionality that I feel is more than worth the price. I'm also a big fan of the Black Star sound font, though personally I think the default Sith font is a better Maul option and that's what my Menaces are usually set to. Black Star is my choice for my Emperor's Hand to accurately represent the attitude of a certain redhead we all know and love.
Anyway, you can't really go wrong with a double Menace no matter what you choose. They look good, they're nicely sized, and they're actually a good deal lighter than I expected. Someone who knows what they're doing should have no trouble performing all sorts of cool displays. Good luck and happy sabering!