On a core i7 with 16GB and a completely fresh Windows 10 install that has never had Firefox on it (so we can't blame an old profile on the machine), Firefox with a single plugin (Keefox) is noticeably slower than Chrome. Just logging into my Google account I saw surprising amounts of basic UI stuttering. Something like Inbox (which is admittedly a pig) loads slowly and scrolls sluggishly.

Chrome, by comparison, is responsive and snappy.

I wish it were different. I really want to like Firefox, but on this machine, with some very basic tests it's clear that, for me, it simply does not compare...