The great northern attaches using a rubber strap that wraps around the riser of your bow, and the wire frame sits "behind" the attachment points on your bow- it's the quiver I had used on longbows for a long time. Nothing wrong with it, but it does add substantial weight on its own and then fully loaded with five arrows you are getting up there.
The Eagle's Flight, as Don said, is almost like there is nothing there. He uses closed cell foam in his hood, the Great Northern uses hard rubber. I like the foam, because I can remove it, cover it with plasti dip to waterproof it to keep moisture off my b-heads, and reinsert.
Because the EFA is two pieces you can use it on a larger variety of bows- the GN will only adjust so much and then only if you buy the adjustable version. Even then you cannot change the angle of the hood or bottom piece- the EFA you can.
I do not like a wraparound style quiver on my TD recurves, and Don has responded to that by coming up with a limb bolt model for TD recurves which I and a couple other folks are field testing and it should be available pretty soon.
Carry a bow up and down a mountain all day and even 6 or 8 ounces will make a huge difference to how you feel at the end of the day when that shot opportunity of a lifetime presents itself.
I get no free quivers from Don, I pay just the same as everyone else, just in case someone is wondering...I just happen to like his stuff as it responds to a lot of the things we DISLIKE about bow quivers- mostly adjustability and the extra weight.
Some folks like Cadillacs, some like BMW's, and some like pickup trucks...it's all good as long as it gets the job done for you!