Beyond that, their success as browser extensions and mobile apps is really just chance (and probably something about their names), as they both do things very differently - AdBlock's quite versatile on desktop where Adblock Plus is simple, but AdBlock has thin mobile abilities where its friendly counterpart has mastered that area. So how will you know which one feels best to install on your computer or mobile device? Simple - check out the differences.
AdBlock (which does not work in Internet Explorer) has an in-depth options menu on desktop. This includes every thing you would need to get tricky with ad blocking, like doing it on one domain only, or turning it off and on either permanently, or temporarily for a given site, as two examples.
Troubleshooting AdBlock is a bit more direct too because you can do that from its main menu. On a related note, you can see all updates (version releases) ever made for the extension from a little window inside that same menu in the support section (just click 'see changelog'). But if you're really curious you should just visit the article, which is all about what a sophisticated blocker AdBlock is - compared to Adblock Plus anyway.
Adblock Plus has a range of ways to block mobile ads where AdBlock has far fewer. This extension is therefore a good fit for a user who, like many, will only care that an ad blocker is installed, and that appreciates the convenience of stopping most mobile ad content the same way as on desktop.