I have the leupold one and that magnet will not slide around. It proved really useful working out a scope alignment issue, that ended up being a probem with the base.
I have never had alot of luck with bore sighting, my fat head makes it hit typically wide right, though now I adjust for it so I push the scope right and slightly down as a starting point.
It is very useful for confirming zero.
I would love to do a comparision to the arbour type, I suspect the arbour type will get you closer on the first shot.