Everybody I can think of uses cometic gaskets, & everybody on this site has said good things about them. I believe that's the general consensus amongst the QRHQ builders also. I personally have never tore an engine apart so I can't tell you from personal experience. I'm sure iceracer could chime in and answer your question since he rebuilds them.

I have had good results with all of the Cometic gaskets except the head gaskets.  I have not found ANY head gaskets for the LTs other than OEM that are consistently good.