Equipping armor is first of all.....well, just a smart thing to do when you're going to run around and fight things. However, some suits/pieces of armor have unique characteristics, and these characteristics can help in various parts in the game.
Name: Cloth Tunic
Description: Simple cloth tunic
DEF: +1
Name: Hide Cuirass
Description: Tanned leather cuirass
DEF: +1
Name: Alucart Mail
Description: Resist fire, lightning, ice?
DEF: +1
What it does: Not a lot by itself, but when worn with the other two Alucart itmes, Alucard's luck will shoot up 30 points.
Name: Bronze Cuirass
Description: Bronze cuirass
DEF: +3
Name: Mirror Cuirass
Description: Polished to resist stoning
DEF: +3
What it does: When worn, Alucard is immune to the "stone" status.
Name: Iron Cuirass
Description: Iron cuirass
DEF: +4
Name: Steel Cuirass
Description: Steel cuirass
DEF: +5
Name: Silver Plate
Description: Silver breastplate
DEF: +6
Name: Ice Mail
Description: Strong vs. ice-based attacks
DEF: +8
What it does: Cuts damage caused by ice-based attacks in half.
Name: Dark Armor
Description: Impervious to evil attacks
DEF: +8
What it does: When Alucard gets hit by a dark/evil-based attack (such as Malachi's swirly ball thing), he takes no damage.
Name: Gold Plate
Description: Gold breastplate
DEF: +8
Name: Lightning Mail
Description: Strong vs. lightning-based attacks
DEF: +8
What it does: Cuts lightning-based attacks in half.
Name: Platinum Mail
Description: Platinum breastplate
DEF: +10
Name: Holy Mail
Description: Strong vs. holy attacks
DEF: +11
What it does: Cuts damage caused by holy-based attacks in half.
Name: Walk Armor
Description: DEF increases with map coverage
DEF: +12 - +32
INT: +5
What it does: This armor's DEF goes up with the more rooms you find. I put it on as soon as I found it out of mere curiousity, and the DEF nearly tripled by the time I had covered both castles!
Name: Spike Breaker
Description: Spike-breaking armor
DEF: +12
What it does: Allows Alucard to walk, run, fly, float or whatever thought spikes without getting hurt.
Name: Brilliant Mail
Description: Increases sub-weapon strength
DEF: +12
INT: +1
What it does: Makes the heart sub-weapons (such as holy water or axes) stronger.
Name: Fire Mail
Description: Strong vs. fire-based attacks
DEF: +13
What it does: Cuts damage caused by fire-based attacks in half.
Name: Fury Plate
Description: DEF goes up when damage taken
STR: +1
DEF: +13 - ??
What it does: The lower Alucard's HP gets (out of his overall HP), the higher his DEF gets.
Name: Dracula Tunic
Description: Embroidered nobleman's tunic
STR: +3
CON: +1
DEF: +14
INT: +1
Name: Diamond Plate
Description: Diamond breastplate
DEF: +15
Name: Mojo Mail
Description: Increases magic attack power
DEF: +15
INT: +1
Name: Axe Lord Armor
Description: Wearer becomes an Axe Knight
ATT: +2
DEF: +15
What it does: When you put this on Alucard, he says "WHAT??", and lo and behold, he's a little Axe Knight! Alucard looks funny when he moves around like this (try jumping!), and the best part of it is when he stands still for a moment: he'll grunt and struggle, trying to get out of the armor (and getting really peeved while doing so).
Name: Alucard Mail
Description: Resists fire, lighting, ice
DEF: +20
What it does: Cuts fire-based, lightning-based and ice-based attacks in half.
Name: God's Garb
Description: Strongest of all armor
CON: +1
DEF: +26