Opera is my go-to browser (PC user). Fast, secure, tons of neat shortcuts. Its only downside is that it can't handle certain plug-ins. I've used it ever since I had a 366 MH processor and it made broadband browsing tolerable in a way other browsers didn't.
I'm new to the Firefox game and only recently downloaded it because there were certain audio feeds that I couldn't access with the other browsers. It's OK. Not as fast as Opera. And to be fair there are a lot of features that I'm not familiar with.
Chrome is also [dang] fast but I mainly use it to access some audio feeds that I can't get with my other browsers because of plug-in incompatibility issues.
I have noticed that Firefox is better than Opera when it comes to timely updating the live scoreboard from ESPN, etc.