Sand is much more natural. Almost every habitat our fish come from has a slower current than would allow for a gravel substrate. It is also much cleaner since it does not require any vacuuming. With adequate flow debris doesn't collect on the surface. With inadequate flow the debris is visible on the surface, not hidden in the substrate. So you know you need to clean it.
It is much harder to remove extra debris from under an undermaintained UGF that it is to just clean out an undermaintained HOB or canister.
Have you used sand? How many tanks? For how long?
It is not ideal in every case, like I already said, but there are very few cases where it is not better than gravel. These exceptions are generally just big fish like cichlids that spit the sand into the filters or something like a large catfish that kicks up a lot of sand into the filters every time it moves. But there are many fish that should be on sand instead of gravel. These include: stingrays, cories, loaches, many cichlids, goldfish, and many others. There are even many cases where gravel is much worse than sand and can even pose a lethal threat to many types of animals (like goldfish, axolotls, and many other fish that can get gravel caught in their mouth or become impacted is they swallow any).
you need to turn over sand, otherwise it compacts and forms gases that can kill your fish and make you sick. now that is a fact.
you can't say that one substrate is better than another. its 100% based upon preferences. corydoras, loaches, cichlids, and goldfish do fine with gravel. in fact, some cichlids should be kept with gravel because they kick up sand so much that it would burn through the filter quickly. goldfish will eat sand. in fact, every fish that i have had eats my sand at some point, but none have choked upon a piece of gravel. also keep in mind that my angelfish has been in a barebottom, gravel, and sand tank. it only eats the sand. o have also yet to hear of a goldfish choke on gravel. sure, they are not the smartest fish, but they are not stupid enough to eat gravel.