Is your device rooted? If so, install AdAway (from the fdroid repo) or a similar host-based blocker. This takes care of a large part of the ad-related misery. I do run Firefox (well, Fennec, really, minus the obnoxious bits which Mozilla has been slipping in recently) on a 4 year old Motorola Defy. The battery lasts for about 5 days so I don't think that bit about FF 'drink[ing] battery' is correct, at least not in my case. I do not have uBlock (or any other blocker) installed as the hosts-based solution is sufficient for now.
Oh man, what a difference a year makes. I gave up on FF when it was a freshly laid turd. I tried it again a few months back on a recommendation from HN. Whoa. They've managed to polish it into a diamond.
You'd have to prize Firefox and uBlock (on my first gen Moto G) out of my cold dead hands.
Firefox on Android is awful. Try to load any mildly heavy webpage (such as Verge) and scroll through it, you'll see how it struggles. (This on a Nexus 5.)
https://play.google.com/store/apps/details?id=org.mozilla.fi...