Which is better?....

It depends on the creature. If you want to go non-elemental it's just fighting the creatures without using any of their weaknesses. When using element weapons find what they're weak too (check armors). Then you will need to make your many different weapons with different elements for creatures. Element weapons help with the damage dealt to the creatures. Affinity weapons give weapons a chance to do something like a critical hit, so you'd do more damage. There are armor that give weapons affinity, or element weapons that already have affinity. For me I would get both just to have things I can switch too, because just using one weapon isn't fun.

I say elemented weapon because it will do extra damage to monsters that are weak against the element. Even if it isn't weak against the element it won't lower the damage.