Sorry folks but though i'm just speaking from personal experience, it's what I noticed time and time again. I've given Firefox multiple chances as my default browser over several years right up until maybe a year ago and the same problem presented itself across different laptops and FF versions (many after in those cases someone told me that FF was FINALLY fixed, oops). Were these laptops heavy duty models with serious CPU, GPU, RAM and etc power? Nope, but they shouldn't have to be for just running a browser.
Chrome on the other hand (and believe me I despise Google in so many different ways) has consistently been okay. Not great, but okay, and certainly better than Firefox. This while having the same browsing, tab and extension habits in both browsers.
With comments like my original above I've always seen a bunch of people come out with all sorts of caveats defending or justifying FF, but personal experience has consistently shown me differently.