Firefox. I honestly don't think Microsoft Edge is shabby either, considering it's the successor to Internet Explorer. I swore by Chrome for whatever reason for about 10 years. I stopped using it on PC over 2 years ago.

Chrome eats memory.
IE was never that good.
Safari is fast.
Firefox was great when it arrived making it very clear that IE was lacking.

Currently using Brave. Best for privacy and revenue generation. Ok in most other aspects, does not have as wast of an add on support as the gigants however.

I've also disabled lots of services, processes on startup or that run in the backgroud and still, for some tasks the computer barely runs faster than my last one on windows 7 even though it has double the memory a faster processor and some other perks,(well the system consumes about 3 GB or more at all times so there is that)  and web browsing has become a challenge in that no matter the browser the memory consumption escalates so damn high that lots of times is the thing that starts slowing down and later i've have to exit and clean everything, when in windows 7 I had browsers with hundreds suspended tabs reviewing them one by one when analyzing search results.

 

Oh the horror of moving between systems yes, I also transferred up some files on ipad and iphone a few moths ago with the help of my sister macbook(that is 2017 I think, but still works like a charm) and then for some days the PC with 10 couldn't recognize the devices, even tough it did before, I think because of an update, later when finally it could, for example the photo import that worked so well on Windows 7 got stuck on windows 10 with their photos app, now that they revamped their photos app again it finally works, on direct transfer some files that had long dir paths send errors when trying to import on windows 10

Firefox was certainly lighter on Mac yeah, it was easier to use there that it is on windows, in fact it was easier to use Safari, Firefox, Opera, and then Chrome, (and the Chromium compiled binaries were also better than chrome but sometimes the dudes that were doing them didn't update for sometime), while on windows i think the performance is  better for Chromiums like Opera or Brave, some say that Edge runs well, but I find it kinda clukny and slow since its trying to integrate with other windows things, and also i'ts kinda shady with respect to privacy so i've just mantain it shut down, I would like to use firefox but currently it's on the bottom of the barrel performance wise(and it was involved in two sudden shutdowns of the system when I was using it).

Opera for almost 20 years now. With the Privacy Beaver Badger extension pretty much as private as Brave, if not even more, but with more additional functions.

To the Opera folks: have you tried Vivaldi? I believe it's from the original creators of Opera, and has none of the Chinese influence behind it that Opera has (if that's something you care about, of course).

Opera on Windows, Safari on Mac and mobile.