I went with aquarium sand because I wanted the black color. Also, at 120-5 pounds (depending on the holiday ^_^;) and living in an apartment, 20lb, 40lb, and 100lb bags are a bit much to handle and store. I know I can lift 20-40lbs if I didn't care about color, but then the left over sand would take over one of my closets. Since 100lbs is roughly 80% of my weight, that wouldn't be an option no matter how much money I had to save. ^_^;
So far, I have no regrets about paying a little extra for the aquarium sand given my level of strength, small size/number of tanks, and pickiness over color. :)