I've found some stuff to be a bit slower on new FF since I made the switch when Quantum came out, but I chalk that up to heavy use of some Google webapps in which the chrome optimizations might have the opposite effect on a different JavaScript engine, and heavy use of containers, which are awesome.[1]

1: At first I didn't know how to get sites to default to a container, so kept having to close and reopen tabs to get the right contianer, but once I figured that out, it's smooth.