Firefox performs as well as chrome 99.8% of the time. The problem is chromium keep implementing things that haven't gone through the spec process fully yet. This causes the following situation:

The other browsers don't implement half baked privacy violating features which Google decides will be a new web API despite objections. Developers build features on their sites using that half baked crap. Users try to use the new features on Firefox and kick off about "Firefox specific bugs" because they haven't implemented non standard APIs.

Safari is its own kettle of fish though and causes a lot of drama. Recently they've caught up a lot in terms of support for most standard features developers want. However there's a big issue with supporting iOS Safari - it's version is tied to the iOS version of the phone. So users with older phones will be stuck forever on older versions of Safari with breaking bugs for things like flexbox. If you're in a market with lots of older phones then you have to spend a lot of time ensuring you support that older browser version. iOS Safari is the new internet explorer.