There are multiple “types” of armor in Chronus Arc, but these “types” are not explicit in the game.
There are several paths through the armor enhancements, but I’ve listed here paths that reach the maximum enhancement within 4 of the 5 different armor types. (The missing type is “elemental” and I did not try that one, nor did I go through the evasion and stats types).
You need all the relevant boost manuals as well as a substantial amount of materials, many of them difficult to obtain, to enhance to the maximum. The best armor type against the final boss is probably the one that increases resistance to abnormal states. A comprehensive discussion of armor paths can be found here.
Protect from all magic. Resistance to abnormal states up
Plate Mail->Steel Armor->Providence Armor
Steel Dress->Protection Dress->Magic-Breaker Dress
Gothic Robe->Battle Dress->Maid Dress
Highest Defense, No Effects
Plate Mail->Mithril Armor->Gold Armor
Steel Dress->Providence Dress->Goddess Dress
Gothic Robe->Magic Robe->Transcendent Robe
Plate Mail->Steel Armor->Ninja’s Outfit
Steel Dress->Protection Dress->Kunoichi
Gothic Robe->Battle Dress->Imp Dress
Plate Mail->Steel Armor->Warrior’s Armor
Steel Dress->Protection Dress->Ironwall Dress
Gothic Robe->Battle Dress->Transcendent Dress