All brands of epoxy work the same, via chemical reaction between part A and part B. There is no "better" brand than another. As long as you mix it correctly–equal parts A and B–they all work just fine.
I use all sorts of epoxies, 5 minute, slow setting, etc., and I use all brands...Devcon, Loctite, Elmers and many more.
I prefer the type that comes in a 2-part plunger, where you automatically get the right amount of A and B when you press the plunger. Wipe the tip(s) off with a paper towel after you dispense the stuff and replace the cap. I've never had any problem with the stuff "drying up", because it can't! Epoxy will only "dry" when parts A and B come in contact with one another, and the 2-part plunger dispenser prevents that from happening.
Like I said, I've used many different brands, and they all worked perfectly for me. I've NEVER tried a brand that didn't work well. If you're having a problem getting epoxy to work, you're probably not mixing it correctly.