I voted leather. Very few of my characters actually wear one kind of armor. My mages generally wear ordinary clothing, and my stealthy characters wear a mix of light armor and ordinary clothes.
My warrior types usually wear a mix, often enchanted with elemental shield. When your armor skill gets high enough, it doesn't make much difference what you wear, so I'll go for whatever look suits the character. My personal preference is for the look of an iron cuirass combined with leather, with no helmet, or maybe a mage's hood. It's rustic enough to be believable for an adventurer who is scrambling around in dirty old dungeons. Full heavy armor seems out of place for that.
One of my favorite characters was a female Nord barbarian who went through the whole game with only the iron cuirass, leather greaves, and leather boots from the tutorial. She picked up a silver claymore somewhere along the way, and that was the whole package.
Fancy armor is for selling to the merchants, and the gold you get is for buying potions, spells, and ale.