Actually, Internet Explorer was a lot better in the RAM usage dept. when I used it for about 10 minutes like 5 years ago (nah maybe a month). It was fast, too. It simply couldn't get it together, though, something was always breaking or needed resetting. Plus, it was genuinely creepy to me, it was so....yesteryear. I find it grim that IE is still usable in Windows 1909 but legacy Edge is dead and buried (unless you clean-install).
Re: Firefox. Reassuring to know that hundreds of millions use it.
To each his/her own.