Latest version does multi-processing, e10s is finally here (though it might still get disabled by usage of certain add-ons, I remember I had to force it to stay enabled).
On performance, in the past it felt sluggish, but now Firefox is fast and for my usage patterns it uses less memory than Chrome.
And one thing I really love is the Awesome Bar, which is a pain point every single time I open Chrome. I have a lot of websites I need to return to and in Chrome I end up searching on Google far more than I should. I guess that's the biggest difference between Firefox and Chrome, as Mozilla does not feel obligated to shareholders to extract ads clicks from you (although I hope that whatever they do keeps them afloat).
Also, tab management. I installed "Tab Center" from the Test Pilot and it's awesome. The experiment is now over unfortunately and the code itself for Tab Center isn't compatible with WebExtensions, but there's work going on to port it and that highlights that Firefox's WebExtensions will be more flexible than Chrome, if they aren't already.
But in the end I actually care more about trusting my browser and its maker to protect my interests. I actually trust Google more than I trust other companies, but something feels very wrong for a company to have so much leverage on me. Which is why, as long as I have a choice, I'll always prefer Firefox over Chrome, or Safari, or Edge.