Wouldn't this also have something, atleast in part, to do with your filtration system?
I have an undergravel filter... hence I use gravel. The sand would get sucked right throught the grid and flood the filters.
I'd love to use sand, as I think it would create a more natural environment. But, I know it's not very compatible with the type of filtration I'm running in my main tank.
If you're not using a UG system, I think it comes down to maintenance, and how you want your tank to look. You need to maintain the sand, as others have suggested. Ofcourse, you have to maintain gravel as well. But maybe not quite as much?
Joe