Guild Wars 2

As a guardian, I use mace/focus and greatsword. Started out with greatsword only in levels 1-15, but then I tried mace/focus and found it to be AMAZING for survivability, but still use greatsword mainly.
But on the topic of greatsword/hammer, i think greatsword is a lot more powerful. For starters, the auto attack is much faster, does high damage, and also gives you might. If you use you traits right(I think 5 in the trait that gives you health and healing) you get vigor whenever you critically hit an enemy. Since greatsword attack is very fast, it is easy to gain vigor, making it easier to dodge and evade attacks. The 2nd skill is a very good AoE attack. I sue the third as an AoE attack and to leap into battle. The symbol can heal you(when traited) and also give you retaliation, which helps a lot. The 5th skill is very good for interrupting enemies, getting ranged enemies close, and dealing damage as well.
Hammer, on the other hand, has more crowd control skills. Immobilize, knock down, and prevent movement inside or out of an area. It’s auto attack does more damage, but takes much longer, so greatsword overall outputs more from auto attack.
All in all, it depends what type of play style you want. Greatsword gives you more mobility, whereas Hammer limits your opponent’s mobility. Greatsword would also probably be better at groups, since all of it’s attacks hit a wide range, and hammer might be better for single target combat.