Guns are great because despite their stats saying they look weak, Guns never miss and they completely ignore defense. The Elemental Shots you get later give them an even bigger punch. I really love the Guns personally. There only drawback is that they are the slowest weapons in the game but they also have better range than most of the Range Weapons. I love using guns to "fish" out enemies in packs from a distance. They're good mob control weapons.

Armor mostly factors in later when you are either covering for an elemental weakness like the Black Masks which are average defense-wise but make you completely immune to Dark elemental attacks (great for undead and Zodiark) or in most end game pieces, to Maximize damage output. Equip Lady Ashe with the Masamune, Magical Shishak, the Robe of Lords, and the Genji gloves and you have a nasty Samurai character with the highest damage potential in the game.

Most of the Armor by end game starts to be built around the weapons you choose to use.