... the guy did a demo on a screw (SS I think) with a stripped head. One end of the bit grinds the hole smooth, then the other end (using the drill in reverse) has little grips that back the screw out. The demo looked fast and slick so I ordered a set of 4 ($25).

I also ordered their seal-a-tube and putty chaser for home, look like good tools to have around.

I've never used any of them, nor the ones you asked about, so can't vouch other than the demo I saw. Look forward to seeing other responses.

Max

There's a video demo at this page that shows it in action. He claims that it works well in brass:

http://www.praziusa.com/grabit.html