I had the opposite experience. Used Chromium for as long as I could remember, then it started becoming too slow and memory-hungry. I switched to Firefox and it's been so much better! It's super fast and uses way less memory. The only thing Firefox is truly a lot slower on my computer is the startup. But the only case in which I start Firefox is after updates, otherwise it's always running.

I'm running Firefox on ArchLinux with the 5.8 kernel and an Intel motherboard with integrated graphics.