Definitely depends on your dress. If it’s floorlength, you may trip on it if you don’t wear heels. The shorter it is, the better flats will look: one reason heels are so popular is because they make your legs look longer, but a short dress will do that already. Just make sure that your shoes are elegant, match your dress, and are comfortable enough to dance in.
I personally love a nice pair of heels though, and I’d recommend that if you find a shoe with a medium-sized heel that you like, give them a go! (but don’t wear them to prom if walking in them is still awkward, because if wearing flats is a faux pas, falling over in heels is a bigger one)