Either work well. It is more on how you put them on as to what type they are. When you assemble them, put a very light bead of RTV, assemble to fit(do not tighten bolts). Let dry, then tighten down the bolts. You get a great seal this way. You don't want to torque down on the bolts while the RTV is wet as the gasket will move from the pressure and you will get huge leaks. But when it is just sitting there the RTV forms a great seal and keeps your jeep from leaving little riminders where you have been.
Another thing to check on all covers is the bolt hole itself. They can buldge inward if the bolts have been overtightened tring to stop a leak. Just look at the gasket surface of the cover to see if it's flat around the bolt hole if the metal around the hole is'nt straight tap it with a ball peen hammer to flatten it out.DP
i use laquer thinner to clean that type of stuff. used to use gas but it's too expensive now. i agree to put the RTV on, but i use the spray on for stuff like that. it puts a very thin even coat on and is much easier to do. plus, you don't have a hardened up tube of RTV when you're done. use a coat hanger through one of the bolt holes in the gasket and as mentioned, let it hang somewhere to get tacky.
I bought one of the $18 rubberized ones and it hasn't leaked since... but then again it didn't even have one previous... just rtv. But seen many cork ones leak, and had them leak in other applications.
nothing wrong with a cork gasket. Theyve been using cork for years and years, and if they didnt work...no one would buy them. I wouldnt spend more money on something if i can get something a little cheaper to do an equivlent job. Ive never had a cork gasket leak, unless i didnt take the time to do it right.
as said above, make sure the cover bolt holes are not bulging and dont overtighten the bolts, try to get them as even as possible and you wont have any problems.