Out of curiosity, I did a little testing with different armors and mid- and late-game materials. I tested chain mail, plate armor, and Armor of Great Health. (Note that because AoGH typically spawns with a +1, all the ones I tested also had a +1.) I used the following metals: Meteoric Steel, Arcanite, Mithril, Illithium, Octiron, Adamant, Valpurium. (I left out lower-level metals because I felt they were irrelevant - who puts on bronze plate armor anyways?) I also ran tests on "soft" armor, including Phoenix Feather, Angel Hair, Dragon HIde, Spider Silk, and Golden Eagle Feather. I checked armor values and dex/agi penalties (as a percentage). Here are my results:
Chain Mail
Material Name AV Weight Penalty
Meteoric Steel 9 14000 10%
Arcanite 11 1600 3%
Mithril 12 10000 5%
Illithium 14 12000 10%
Octiron 17 1800 5%
Adamant 21 20000 10%
Valpurium 25 6000 2%
Plate Armor
Material Name AV Weight Penalty
Meteoric Steel 15 28000 20%
Arcanite 18 3200 6%
Mithril 20 20000 10%
Illithium 22 24000 20%
Octiron 27 3600 10%
Adamant 35 40000 20%
Valpurium 40 12000 5%
Armor of Great Health +1
Material Name AV Weight Penalty
Meteoric Steel 12 35000 40%
Arcanite 14 4000 13%
Mithril 16 25000 20%
Illithium 17 30000 40%
Octiron 21 4500 20%
Adamant 27 50000 40%
Valpurium 31 15000 10%
Soft Mail
Material Name AV Weight Penalty
Phoenix Feather 5 400 0%
Angel Hair 8 600 0%
Dragon Hide 10 5000 2%
Spider Silk 11 600 0%
GEF 18 200 0%
Soft Plate
Material Name AV Weight Penalty
Phoenix Feather 8 800 0%
Angel Hair 14 1200 0%
Dragon Hide 16 10000 4%
Spider Silk 18 1200 1%
GEF 30 400 0%
Soft AoGH +1
Material Name AV Weight Penalty
Phoenix Feather 7 1000 1%
Angel Hair 11 1500 1%
Dragon Hide 13 125000 8%
Spider Silk 14 1500 2%
GEF 23 500 1%
Valuable Mail
Material Name AV Weight Penalty
Silver 3 21000 10%
Gold 3 40000 3.3%
Sapphire/Ruby 15 8000 10%
Diamond 18 7000 10%
Valuable Plate
Material Name AV Weight Penalty
Silver 6 42000 20%
Gold 5 80000 6.6%
Sapphire/Ruby 25 16000 20%
Diamond 30 14000 20%
Valuable AoGH +1
Material Name AV Weight Penalty
Silver 5 52500 40%
Gold 5 100000 13.3%
Sapphire/Ruby 19 20000 40%
Diamond 23 17500 40%
Shirt of the Golden Eagle +10
Material Name AV Weight Penalty
GEF 40 100 1.2%
For reference: INT requirements for various materials. (For hardening. Remember to add 5 if you want to SoCM.)
INT Materials
15 Meteoric Steel
20 Arcanite, Phoenix Feather
25 Mithril, Illithium
30 Silver, Gold
35 Angel Hair, Dragon Hide, Sapphire, Ruby
40 Octiron, Adamant, Spider Silk, Diamond
45
50 Valpurium, Golden Eagle Feather
From this we can draw some conclusions about the usefulness of various armor types.
Chain Mail: Useful in the mid-game, but not really worth it outside that. Arcanite and Mithril chain mail are great in the 20-35 INT range - low penalties, manageable weight, and superior AV to soft armor - but below 20 INT the weight and penalties are too high, and above 35 INT the soft plates have superior AV and almost no penalties.
Plate Armor: Great AV, but nasty weight and penalties. Not worth it until you can get the Arcanite series - Arcanite plate is easy to acquire, and is comparable to the 35 INT Spider Silk soft armor. Mithril plate may not be worth it, though; however, at 40 INT, Octiron is a solid option, and at 50 INT the Valpurium plate is a rival to a GEF armor.
Soft Armor: Excluding a gap between 20 and 35 INT, soft armor are probably the best option. The almost absolute lack of penalties is hard to beat, and the 400 gram GEF armor is pretty excellent.
Soft Chain: I just ran these for fun. They are useless.
AoGH: Don't. Just don't. There is nothing redeeming about this armor, whether soft or hard. Double the penalties, 25% more weight, 25% less AV; "balanced" by more HP, which means nastier enemies spawning.