I've always had good luck with cork gaskets even the cheap ones. I make sure everything is clean and oil free, use rtv to attach the gasket to the valve cover and most of all don't over torque when you install the covers. After some run time go back and check the torque,again don't over do it just make sure they didn't loosen up.
I bought a set of the Fel-Pro perma dry gaskets a couple years ago but haven't used them yet.
I normally get about 4 to 5 years out of the cork gaskets before having to replace them.