I know most of the answers here, prefer Gecko over Chromium because Google is a monopoly, but honestly I would like to make the switch, the bad thing is that I still find the Firefox interface on Android old, I know it seems a bit silly to risk a little privacy for a comfortable and visually pleasing interface, but recently I saw that Chromium forks are even more secure than those using Gecko, that’s why I still use Cromite
I take this opportunity to say that possibly the solution to this is WebLibre, a browser based on Gecko which is exactly what I’m looking for, unfortunately still in alpha but from what I’ve seen it’s on the right track
I mostly use Firefox because it lets you bookmark a page without overwriting an existing bookmark. I have a lot of bookmarks and they sometimes need to be in multiple folders, but Blink-based browsers only let you create duplicates by manually copying a bookmark and pasting it elsewhere.
I’m finding certain security features being lacking from Firefox to be annoying. I should be able to set JIT javascript compiliation and DRM to be opt-in on a per-site basis considering the security risks in those codebases, especially considering the weaker security of the Gecko engine.
I’m also concerned about the prospect of the only browser engine besides Webkit being Blink, but if that were my only issue I could spoof my user agent.