Chrome is the fastest browser for YouTube because Google intentionally made it slow on other browsers. So, sometimes this speed is just the result of monopolistic actions.
I think this is the value of others like Vivaldi and Microsoft standardizing on the Chrome web page engine. They will strip away any ad company privacy layers. Only Firefox is truly free at this time and Safari doing whatever they do.
Safari's implementation of AdBlockers is the same as the one that's planned and criticized for Chrome - isn't it a bit wierd to bring it into this debate?
For me Chrome is the fastest browser all around. It may not be substantially better than Firefox anymore, but it's still the best. The day it stops being the best I will consider shopping for another browser.
(I mention Firefox specifically because it's the only browser that uses something other than webkit/blink, now that Edge is out)
[]Perhaps that will change once they nerf ad blockers.