I just have a Kuryakyn 4220 Chrome Universal Helmet Lock mounted on my highway bars. Works for my half and full face helmets. Like you said Dave, if someone really wants it they'll get it no matter what kind of lock you have.
I like simple and mine is the simplest for me.

Have a heart that never hardens, a temper that never tires, a touch that never hurts. - Charles Dickens