Depends on how you play. The advantage to traps is that they affect any monster regardless of resistances/protections. The disadvantage is that you have to set them when they are out of sight, then lure them into the trap. This doesn't work so well with some spell casters who like to stay put, and they tend to be the people who have the best protections.
I like giving Yoshimo 100% in traps then setting traps on the spot where liches will appear. It makes Kangaxx's quest much easier.
