If you're comparing daily use browser tag includes a lot of extensions with another browser that's empty - the latter will won.
Then you start moving your stuff, you install extensions and while fighting with your habits from old browser ux you collect history, cookies and all that stuff.
Then some time passes and you're looking back at your old browser, now with cleaned profile, so shiny and fast :)
What extensions do you use that make your browser slower? I only use HTTPS Everywhere, which has no effect, and uBlock Origin, which makes most webpages much faster, so I don't see how this is true.
Then you start moving your stuff, you install extensions and while fighting with your habits from old browser ux you collect history, cookies and all that stuff.
Then some time passes and you're looking back at your old browser, now with cleaned profile, so shiny and fast :)