I use Firefox exclusively on my home computer and I use both Chrome and Firefox on my work computer. Chrome for browsing and Firefox mostly for web development. Firefox doesn't seem appreciably slower than Chrome as far as I can tell.
It might be different on an Android phone. I use Firefox with UblockOrigin and PrivacyBadger on my phone (to lower my data usage) and it feels slower than Chrome, but I think that's probably because Chrome on my phone doesn't have any plugins.