Solely based on the use of resources, tests that I ran years ago showed Chrome to be the best, but it's been a few years and my findings are likely outdated.
As with software in general, the further they develop, the more they work toward taking advantage of more powerful processors which increases resources, so as much as the general pop would disagree with me, when you have a much older system, it is better to go to a site like oldapps.com and download an earlier version of the software. In the end (specifically with browsers) this could cause issues because the language used for displaying websites changes as well, making some sites not as comparable, but what good does it do to have the latest model when you can only get it to creep along?
