They were all the rage when the gun rags ruled the information scene back in the mid-90's. They were counter-intuitive when one considered the 1986 Miami shootout, but so were ultra-light bullets -- yet they were also the rage...Certain authors (who I won't mention...don't feel like going down that road) used to make bold claims about their "research" which they claimed proved the efficacy of light and fast, pre-fragamented ammo. It was later shown that they pulled it all out of their exit-holes and thereafter, heavier bonded JHP's became the norm for recommendations for defense ammo.
If I'm not mistaken, Mag-Safe and Glaser merged and are now owned by the same company. They are pretty much not good enough at penetration and are not considered very effective when compared to heavier standard bonded JHP's. They'll give the target a very bad day, but all else being equal one would make their hits count more if it was completed by a heavier JHP.