I can say that there are more types that just what you've listed.
I don't want to give spoilers, but as my curiosity got the best of me at one point, I used a certain 3 letter command and ran around a fort slaying those who were obviously stronger than me. I do this whenever I test a new mod to get a feel for the difficulty, to explore for the sake of exploring, and because I have fun role-playing a demi-god from time to time. Anyway, long story short, there is far better light armor. It is silvery, shiny, and gives a minimum bonus of +3 at level 28 light armor.
This leads me to believe that as we get further in the game the armor choices will diversify further.
Also, more armors can always be modded in. The world is more difficult and therefore more important in my opinion.
P.S.: The brutal, honest truth about the armor skills is that as long as they are about the same (EG: Heavy is 26 and Light is 28) armor from the same tier, regardless of type, will have relatively similar defense values until you pass level 45ish. This is, of course, just in my experience.