Ranked in these QuestionsQuestion Ranking
Pro Avoids awful looping problems on Firefox one sees with Adblock Plus and uBlock
Pro Completely free
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.
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.
Like any browser extension it slows down your browser.
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.