What's the user visible tradeoff between "an average page is so laden with advertising and tracking nonsense that it loads slowly and is covered with crap, but

What's the user visible tradeoff between "an average page is so laden with advertising and tracking nonsense that it loads slowly and is covered with crap, but that crap all renders real fast" vs "JS renders at 1/10th the speed but only the stuff you want to look at?"