with a tank you can wield a sword/mace and shield, aaaand a two handed sword. so if you need to put out a bit more damage, just switch over to the great sword. tanks are fun and all, but a bit boring for my taste.
tanks are amazing for pulling and holding agro also, not as much as the glad.
Glads on the other hand are supposed to be the main DPS in the game. they wield a two handed polearm, greatsword, or two swords. my fav is a glad just because i like pwning ppl in pvp haha. glads are able to tank for a short period of time, but if it's something strong, you better bring along a cleric, or chanter to help you out, as things can get heated in a blink of the eye.