Personally, I don't think any of them work that great. I'm real fussy about sticking things in my barrels and since none work really that good I've started using the Leupold magnetic ones. They work okay. As good as any, I guess. In reality, I can get closer by sighting down the bores and aligning the scope. But that wouldn't work on some actions, of course.
One of the best uses I've found for the bore sighters is to check a scope out. You can easily tell if it's adjusting as it should by watching through a bore sighter as you crank the knobs.
By the way, the magnetic ones work on stainless barrels, too.
Mike