For multiple reasons I use firefox, you have more control and power and it is rated by far the fastest at its core.
But it all relevant to what add-ons and extensions you use (+ the actual version update your using which can certainly affect speed). Chrome may seem faster because, I doubt many people add-on to it. I think whether all Firefox, Chrome, Opera - the native tools are in place and you can extend, perhaps Firefox the best.
I tried Chrome before, but for me it lacked and I forgot the major problem I had with it. Firefox by default has always since its inception been the most responsible and best at rendering pages accurately (historically when that sort of thing mattered, i guess).
For example with Firefox you can have great power, but with that comes great responsibility - that is why Chrome and Opera don't have expansive add-ons and extensions - they will not get penalized by the public for any speed issues. Firefox you can have safe, non-privacy invasive tools concerning what matters in development, for most roles/jobs. Oh and what browser has a safe password manager system - not cloud-based but local, encrypted, etc -only one -Firefox. It's helpful to have one if you manage many different local environment systems. I've done a mass browser testing recently, ended up coming back to Firefox regardless of periodic and frustrating memory leak issues in v36.
Like I said, everything is relevant and browsers are still developing to adapt and adopt new standards or practice and features. The last few upgrades on Firefox have been horrendous concerning massive memory leak but all browsers have memory leak issues and are no better.
Thus speed is all relative. If you want robust development browser, cross-platform, "web-cooperative" and support/use open-source, I'd say use Firefox - always been design and developer safe and friendly and you have full-power capacity.
PS. Firefox has web developer version but I will not support it - it is in beta but I don't recommend it at this time after testing twice.
Also, unfortunately, browsers for designers-developers, if you are looking for tools, are still lacking in (edit:) anything BUT a base sense, beyond what exists as a few Firefox add-ons. RELATED: In addition to mass browser testing I wanted to settle and make up my mind on a current coding editor or IDE. For me on my RAM-lacking sad system, I need both good functionality and tools without any missing major elements + extras and speed + "lite-ness."
For my kind of dev, the choice environment editor + browser platform for all the above reasons is hands-down Firefox + Sublime Text (+ Chrome, Opera Next Beta, and Safari for testing and tasks services). Both cross-platform, lite and extensive and even portable.
It's fastest and most powerful, extensive, custom and productive browser/edit combo.
[ed. note: giantcarrot last edited this post 6 years, 1 month ago.]