Both, for me. The COP in Lincoln refuses to sign off on NFA items, so a trust was my only option. It also specifies what will happen with my items in the event of my wife or's I's death. I don't have my non-NFA items in the trust but I've considered it for that reason.
Another advantage if you have NFA items is that it allows all trustees to have physical possession of the items. My wife can take the SBR out shooting without me, since she's a trustee - if I had a stamp only in my name she couldn't.