i have used several different types ranging from the cheaper dollar store brand to Boston aqua farms and for durability i choose the Boston aqua farms. the cheap stuff seemed to only make two or three frags and the tube would be empty and a week or two the frag would come unglued.
Maxi-cure, but I get it at hobby shops. Like Colpar Hobbies. They usually have it for less than the LFS. I have heard good things about EcoTech's new glue, but haven't used it.
I'm using loctite gel right now. So far I like it, it works great for sticking stuff to rocks. Give plenty of time to get it in the water and stuck with out getting all over the place.
I have boston aquafarms, but it is a bit runny for me, since I'm always gluing things to rocks in the tank. I'm sure it works great for gluing frags to plugs though. I use loctite and put a layer on both sides of epoxy putty, ram it in, hold for 30s. Glue 10 one week, re-glue 3, next week, then 1, then 1 then 1, then maybe eventually they hold! Seems to be the exact same story no matter what brand of glue. Doesnt help that my urchin picks up frags and carries them all over the tank.
Edit - Ok I guess I take it back. I'm out of loctite and have been using the BAF stuff all night and at second look, i'm pretty sure it goes a lot farther per dollar than the loctite, and has been working well. Also the tube doesn't clog as much.