Taking on the big three, Solid copper, solid stainless steel, and oem MLS.
Pma1123 told me awhile back that he had one blow out on him on a long trip. Now if I had know this before I had bought it, I never would have used it. I figured, what the hell, why not and used it. It was a mistake.
Solid stainless steel
It went in and came back out in one piece, the problem is that it's so hard that it doesn't seal worth dick all. Mine leaked, a small leak just enough to cover the top of the turbo and water pipe with black soot. RRE strongly recommends using the seal ring with it because of that. Most people port out the step completely and if you use FP's race manifold like me, there's no step to begin with.
The best in my opinion, strength of steel plus some crushability to seal. I found a place that sells the 7cm oem evo gasket for $9 a piece (with $10 shipping) on ebay, still cheaper than the $30 without shipping most places here in the us want.