I'd assume it would all be the same whether plastic or aluminum. I think the majority use aluminum, that's what most info is based on. I'm not a gutter man, but just had seamless put on ours after we put on the new roof. Looks great and the hangers are hidden, ended up around $4.50 a linear ft. for labor and materials. Also something to think about if your in a cold climate is the plastic ones becoming brittle in the winter and cracking or breaking.
Brian