Its a big difference in play style between. Zerkers keep hate by just going all out on the mob, they don't get a lot of hate reduction buffs or abilities that have a taunt effect attached.
Guardians are a lot more about finese and knowing what skills to use when. They don't do practicly any damage, but get a lot of hate related buffs and spells.
If you're just starting off I'd go with zerker. Its easier to get the hang off and become good with.