I prefer Firefox over Chrome just for the amount of customization and plugins that are available (Chrome has almost zero customization). There are also several plugins that I love in Firefox (Proxy on/off button, SkipScreen, and more.
However I switched over to Chrome for the past 2 weeks because my Firefox was giving me some trouble (mainly a few webpages were loading incorrectly for some reason - probably since I installed the beta alongside it, not sure). I've also got a few quirks with Chrome in how it operates differently from firefox but I manage with it. I don't like how Chrome often shows a white page when loading different/new websites or pages, FireFox doesn't do that.
In terms of performance, I don't notice Chrome being any bit faster than FireFox in real day-to-day usage and loading of webpages. I don't worry about RAM consumption as I have 6gb of RAM and loading both browsers up from cold boot is about the same