Ive had a steel trailer for years, no problems, small rust. I've used my friend's alum. trailer. Only trade-off with the alum. is it's much lighter without a load and tends to skate on the highway and rough roads.
Our open trailer (steel) has a solid deck which makes it much more versitile for lawn mowers, tractors, quads, etc. We use it for a lot of equipment. Most alum. trailers i've seen have an open center, which limits them to just cars and larger vehicles.
I would def. say buy alum. if you're only using it to move the Viper to and from. Might think about steel if it's multi-use.