Rubber gasket vs. a cork gasket

Hello all,

I was wondering which gasket for a valve cover is better: rubber or cork? Or is it just more of a preference? Common sense tells me that a rubber gasket would be better, but wanted to get some expertise before I change it out.

I noticed that ther was oil under my car, and that it was dripping down the side of the block. I made my first attempt at ever installing a valve cover gasket. To say the least, I didn't do a very good job, and she is leaking again. I made a rookie error of thinking that tightening the bolts even more would make a better seal. There is that common sense again.:oops: Anyhow, I want to right my wrong and do it again, but I want to make sure I get the best gasket for the job. The original gasket was cork, and rather new, as well as the last one I put in. I suppose that is why I am leaning towards a rubber gasket.

The engine this is for is a 225 slant 6.