Heavy armor: All pieces, considered the Imperial Legion "uniform", are heavy armor. Also, all pieces of armor given to you as a reward for completing Imperial Legion quests are heavy armor. Therefore, if you play a legionaire then Heavy Armor skill is a
must for you.
Also the best armor in the game is heavy armor, including armor artifacts (with one exception). Therefore, a good value of the Heavy Armor skill is highly recommended.
Medium Armor. If you play plain Morrowind without special mods then you can ignore this skill almost completely. It's good only for improving your Agility stat.
There is only one piece of medium armor in the game, which is worth of mentioning - Ebony Mail. This cuirass is a quest item/reward of one Temple quest and it is unreachable otherwise. Therefore, if you aren't a member of the Temple then you cannot get Ebony Mail.
Even the light armor in the game is better than the medium armor! Therefore, medium armor = added weight plus less protection.
Light Armor. There exist a very efficient light armor in the game - the Glass Armor. It's better than any piece of medium armor (except Ebony Mail), it's light and very nice. Only Daedric Armor (heavy armor - and really heavy
) is better. Well, it's also expensive [img]graemlins/hehe.gif[/img]
I recommend the Light Armor skill because the light armor will be your first armor - unless you become so strong that heavy armor will not overweight you.