As mentioned before - I'd also go for Palemoon. I was using nightly Firefox for very long time, but it started to by painful experience, then I switched to Aurora, after few months back to nightly and then I decided to stop this experimenting and moved to Palemoon, which, in version 15 is a lot faster for me (not only my feeling) than any version of Firefox (release, beta, aurora, nightly).
I was trying to move on to Iron (shit-free version of Chrome) many times, but always ended up on Firefox again. Chrome is just way too simple and dumb. I must say that Chrome is more responsive and the UI is smoother than Firefox, but comparing to Palemoon it could be almost the same.