I don't have any scientific opinion, but I have used them for over 10 years in my race car, and my engine has worked very well. My builder also recommended them, and I trust his professional opinion as well.

That being said, they may not offer any real advantage, but you never know..

I've been reading some design engineering books, and the loss from ring friction is much more important that leakdown. Its better for racing to have rings that leak some but have lower ring tension than the other way around.