I have done quite a few jobs using the GAF Liberty system and have not had a single issue. I have been using it for about 5 years now. So in my opinion, GAF is the way to go, simply because I have had nothing but good experience with it.
Since I haven’t used the Certainteed I can’t comment on that.
I am no fan of GAF products myself, I have seen their shingles fail prematurely on more than one occasion.
Even when properly applied with adequate ventilation…
I do however think that Ruberoid is an excellent product.
I prefer Brai or flintlastic but will not hesitate to use Ruberoid, it is a good product.