I don’t know about FF (though I’ve heard it’s suffered from bloat in the past few years), but Chrome is relatively lightweight. UNLESS...
Unless, you install a bunch of customizations and plugins. Then it’s got to go out to the cloud to get all of your junk before it starts up properly.
I don’t bother with any of that, and Chrome runs like greased lightning on my computers. HOWEVER, I still mainly run IE because of one feature: the drop down list on the address bar that shows recently visited websites.
I never could go full on Chrome because of that one feature. The rest of my family, including my little-old-lady-user wife, swears by it though and have pretty much abandoned IE.
Chrome is definitely better than FF memory wise. I need to completely dump anything from the Mozilla group anyway.
I’m looking to see how the MS Spartan browser stacks up, or I may just use Opera for my back-up browser.