First of all...
User-friendly, Efficiency, Privacy, Customization - that is why I use PM.
And a goal of topic:
Just a small issue: don't work pref browser.newtab.preload
i.e. new tab opening causes content area blinking regardless from this pref in about:config
PM 26.1.1-x86-Portable, OS 7 x64.
For discussions specific to the Portable version of the browser.