When comparing uBlock Origin (as a Firefox addon) vs AdBlocker Ultimate, the Slant community recommends uBlock Origin (as a Firefox addon) for most people. In the question“What are the best ad blockers for Android?” uBlock Origin (as a Firefox addon) is ranked 4th while AdBlocker Ultimate is ranked 13th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Fastest loading times
Pro Promised to remain commercial interest free
uBlock will remain free from any commercial as stated by the creator. uBlock is meant to be strictly for the users and completely free.
Pro Completely free
Pro Best Youtube ad blocking
Pro Free and open source
Anyone can improve and audit the code.
Licensed with a gplv3 license.
Pro Supports most popular browsers
AdBlocker Ultimate works on Chrome, Mozilla Firefox, Opera, Internet Explorer, Safari and Yandex.Browser.
Pro No acceptable ads
Unlike other adblockers, AdBlocker Ultimate doesn't have any whitelisted websites, ad networks or advertising agencies.
Pro Avoids awful looping problems on Firefox one sees with Adblock Plus and uBlock
Cons
Con Doesn't block background ads yet
Ads that replace the background image of a website are currently beyond the scope of the ad-blocker, but the functionality is planned to be added in the future.
Con Just a browser addon
It is just a browser addon so it will only work with the supported browsers and you have to install it for all browsers separately.
Con Element hiding helper has occasional hiccups.
Con Memory hog that gets worse the longer it runs
Happened with 64-Bit Firefox 62.0.3 running on Desktop PC with 64-Bit Windows 10 Pro with 8GB of RAM.
Con Slow
Like any browser extension it slows down your browser.