Glass is the best common light armor type. A glass helm gives 144 or so armor, while bound helm only gives 80. The best items in the game are the rare items. Helm of Oreyn Bearclaw I heard is the best helm in the game. It's heavy armor, though. It weighs 10 lbs, but I think it's well worth it. I don't know what the best light helmet is, but I don't think it compares to the Helm of Oreyn Bearclaw.
Helm of Oreyn Bearclaw
Type: Helmet, Heavy Armour
Armour: 261 - (117 more then glass)
Health: 900 / 900
Fortify Agility 40 Points on Self
Fortify Endurance 40 Points on Self
I kill two dwarves in the morning, I kill two dwarves at night. I kill two dwarves in the afternoon, and then I feel alright. I kill two dwarves in time of peace and two in time of war. I kill two dwarves before I kill two dwarves, and then I kill two more.
I may be bad, but I feel good.