That's a good question, because I've seen AM packaged on both spool types. But I think there's a 99.44% chance that it's the same material.
As for the question, I haven't tried Powergrip yet, but I now use Angel Majesty .015 exclusively for everything except my end servings where I use Halo .007. Halo is all Spectra or Dyneema, so it's really strong, which makes it good for end servings. But that's about all Halo is really good for, IMO. It's pretty mediocre for much else, particularly anything that has to repeatedly bend around a sharp corner. I used to use Halo .014 on everything, but it always always separated on my buss cables on my PSE. No matter how careful I put it on or how tight I made it, it would flatten and start separating pretty quick, in a couple hundred shots.
Angel Majesty, OTOH, will outlast the string itself and absolutely will not compress and flatten on something like a PSE buss cable going around that sharp corner on the lower mod. I have it on my current PSE and I've lost count of how many shots I have on the buss, but with no separation at all anywhere.
It's also an ideal center serving because it just plain won't wear out where the nock goes....
AM is a blend of polyester and dyneema impregnated with a resin of some kind and all that i think is the secret to how resistant it is to flattening and separating. Powergrip is a similar formula, so I would expect it to also be really good for buss cables and sharp bends.....
lee.