I started out with OEM SS grates on my 2000 vintage Weber Genesis Silver B. Those were really good. Only drawback was that my wife was constantly bugging me to keep the SS grates completely shiny all the time. Which is basically impossible to maintain if you use the grill.
I later replaced them with the heavy OEM PECI grates, which I liked better. And the all-black all-the-time color satisfied the mrs.
Replaced the PECI with GrillGrates last year, and like the GrillGrates the best by far. Also all-black all-the-time once they get seasoned.
I've seen LM's critiques of the GGs, and just completely disagree with him on every point. IMO the only drawback to the GGs is the cost. Due to the cost I started out with just a few panels as an experiment. Then quickly upgraded to the full replacement.
Being able to use the other side of the GGs like a flat top is great. Best way I've found to do my steaks with a Pittsburgh-style black and blue sear.