For significant periods of time in the mid-late 00-s to mid 10s, this just isn't true. Firefox's plugin, process and memory management was significantly worse than Chrome until relatively recently. As a result, for memory limited machines (all of them - remember, 4GB was considered huge), Chrome was the only real choice. I personally gave up on FF for 10 years from 2011 or so because I was sick of the plugin manager crashing and taking the machine with it.