So it means that firefox stands out from all the browsers and is the best ?
If i open 20 tabs on google chrome and firefox, which browser which be less resourse hungry and by how much percentage the one is better than the other ?
Chrome has a well deserved reputation as eating your RAM like there's no tomorrow, but things can vary massively on different hardware set ups and different operating systems. If you want accurate results for you, then simply download both, open the same 20 tabs in each, then open task manager/activity monitor/system monitor and see which one is using more resources.
Having said that, there's a lot more to consider when deciding which is "the best" browser than which is the least resource hungry. As long as you are running a fairly modern machine, then you shouldn't really notice any difference in system performance between different browsers. What is far more important is that Firefox is by far and away the best browser (not considering Tor) in terms of privacy, security, anti-tracking, anti-fingerprinting, and so forth. Chrome is literally spyware and sends
everything you do online back to Google for collection, analysis, and sale to third parties.