I've always been a sand person, but beyond the big argument of cleanliness, my deciding factor was the types of animals I could keep:
With sand:
I could keep more wrasses, and certain inverts that like shifting sand around that probably wouldn't thrive as much on a bare bottom, like nassarius, conches, cucumbers, some brittle stars, etc.
Without sand:
You can keep more corals on the sandbed! You really can't place some coral right on sand since the grains can irritate and kill many LPS and SPSs, but now you can place them right on, and some can encrust right onto the floor, which is quite an amazing look. (with chalices and favias)
I wish there was a nice hybrid; maybe a dropoff tank with the deeper side being sand, and the top being barebottom? but it's only a matter of time until sand gets to the top portion.