Cyberfox is my personal choice. I've used every browser on the internet (I can't help it, I love testing). Intel seems to work best with Chromium Blink engine, AMD seems to work best with Firefox Gecko engine. I haven't tested every processor out there though, this is just based on what I have which is dual and quad core AMD's, single, dual, and quad core Intel.
Whatever your processor, I can say with some degree of confidence that Cyberfox will run better with it's custom builds tailored to Intel/AMD 32/64bit than if you used stock Firefox. Waterfox runs like crap on all my systems (not saying it's a bad browser), Palemoon is faster and more stable than stock Firefox but I've had compatibility problems with some extensions.
Opera stalls too much on my system and don't have native support for Xmarks without using the addon that allows you to install Chrome extensions and it has too many problems when using Xmarks with it. Vivaldi needs much more work but should be a promising browser. One that I will heavily consider using when in beta/RC or finished. Internet Explorer I use to download other browsers when I have a new system install. It's a sturdy well built browser but is too vulnerable in my opinion. I don't trust Google and therefore can't trust the browser. Torch is "ok" but doesn't have integrated translation support or have the latest Blink engine so I don't care for it. Maxthon is stable and has built in adblock but isn't nearly as fast as Chromium and Firefox based browsers. I've never been impressed with Trident engine browsers - Webkit is ok I guess.
The rest I simply don't care for or trust. My rant would go on forever if I stared talking about the rest.
Disclaimer: There really is no "best". It's about opinion, personal preference, stability, and performance on ones computer configuration. You yourself also trust who YOU trust and shouldn't let others sway your opinion unless there is a security risk involved with the browser in question. Like all could agree that Internet Explorer isn't a very secure browser, especially when compared to Chromium and Firefox based browsers.
