A lot of it comes down to your wants.
Lots of people swear sand is easier to keep as debris just sits on top. IT does take some technique though to use a siphon/vac properly to be able to get the debris up without disturbing too much sand. So some people find this too much of a pain.
Most find sand looks better, more natural and unless you are buying specialty sand it seems to be cheaper as well IME of comparing prices.
It can be a pain to prepare for your tank. Needs to be rinsed well, some sand needs it far more than others, like play sand. Then you also have to allow it to settle and it can be a pain with some different equipment. Always a good idea to keep filters unplugged when you have sand floating about.
If it's not a planted tank you will need to give the sand a stir once in a while to release any gases that may build up in there, where gravel doesn't have the same issue.
Mostly it's a personal choice, everyone has such different opinions on this but sand seems to be the biggest preference I find