I like a heavier sand like aragonite that helps keep ph balanced, is small enough for burrowers, big enough not to get blown around.
Makes the tank look natural. I've done barebottom and algae attaching to it as well as detritus blowing across it doesn't look too nice, plus theres a bit of reflection off the bottom glass that looks un-natural.
JMHO.
BTW, I use Carribisea Special Grade Reef, will never have a tank without it at this point.
If you are using acrylic I say no sand. Glass yes.