Last benchmark that showed real benefit to users was ACID test. Telling off about the trash that IE always had been.
Nowadays, gains are marginal on JS engines and rendering, while devs fall on same mistakes of old, relying on frameworks' magic to pull it all out, regardless of things like NPM dependency hell, lack of caching strategies, linting and so on. We had ugly images for a long time just to ensure no heavy resources were used; now everyone brute-forces networks because at least it's not a stream.
It seems to be more about how much are you being exposed/sold by your browser+plugins (or how some service workers are killing your machine, go figure why you need 1GB RAM to make web outlook/teams/whatsapp work).