My in-laws has aluminum siding and after about 10 years swapped it out for steel (under warrantee). They wanted NO maintenance and now they have it. The aluminum was denting, they live in an exposed area and a branch blowing in the wind would hit the house or one of the many grandchildren throwing things would dent the aluminum. They say the steel is much more quite than the aluminum was and hasn't dented yet.

We have insulated vinyl siding and I am happy with it so far. Not sure how the insulation helps, but it holds its shape better than our last home with regular vinyl siding. The regular stuff we had ended up with warping or bowing in and out, strictly it was fine, but looked funny. You had to look right down the side to see it, but it was weird. I would think just about all of them are very little maintenance.