I have used both the G5, and the NAP Hellrazor. I found through my own limited testing they both shot very well. THe G% seemed to be the tougher of the two, in that the shank of the Hellrazor had two failures where it bent just behind the blades upon impact.
The G5's I used were the SS version, and I found them to be a bit of a pain to resharpen. THe thing I DID find however was that even though they didn't feel sharp like a knife blade or straight razor, the wider angle on them they were actually quite sharp and held the edge fair. There are a couple of fine step by step sharpening tutorials that I found which helped to bring the edges up to a more razor like edge. One is to sharpen it like a Woodsman, and there is an excellent video by Three Rivers Archery on Youtube. After following their procedure I followed up with a couple of diamond hones of finer grit to bring them up to the razor type edge.
The only issues I had with this type head, was I heard a slight whistle or hiss when shot. Not that this made much difference on the hogs I used them on, but it was noticeable. I also found they didn't quite tune as easily for what ever reason with my field points. I used every tried and true method of tuning and had several other heads which shot point on, but these seemed to have their own idea of where they wanted to group.
I eventually switched to the Razor Trick and haven't looked back. this isn't to say they won't work well for you, just I was looking for one type head that would work equally well across three different bows, arrow spine weights, and draw weights.
Good luck