There is no major difference between retro looking prom dresses and original vintage dresses at first sight.
It is up to you which one you buy, each of them have good sides and bad sides as well. Original retro dresses can be very expensive, depending on the age they are from and the material they are made of.
They can go up to a few hundred dollars while reproductions are usually much cheaper. However, if you buy an authentic vintage dress, you will own something very unique, rare and valuable, because it isn't easy to find these dresses any more nowadays.
Vintage looking prom dresses are mostly for those who aren't necessarily crazy about the vintage style, but they would like to try something new, to wear something one of a kind, something that is more stylish than the other dresses they see in shops.
If you belong to the group of people who like to try new things from once in a while, such a dress will suit you. On the other hand if you love the vintage style and you would like to look like Marilyn Monroe on your prom night, it is better if you look for an authentic vintage prom dress.
Vintage looking prom dresses are mostly made of silk, satin or chiffon but they can be made of any other fabric as well. They can be found in many colours, depending on the decade they were inspired by. However, the most common vintage colours are the following: baby blue, jade green, black, cream, white, ivory, black and white, dark red, purple, pink and peach.
For a prom you should either choose an elegant black dress, that will make you look even more slender than you are, or a more lively colour such as pink or purple.