Well, first of all, you can block YouTube ads in Opera (which is the point of this thread). Secondly, it uses much less RAM than Chrome, which makes it better for slower PCs. The reason Chrome needs so much RAM is because before opening a webpage, it tries to run it in like ten different processes for safety purposes, which is pretty redundant considering everyone these days has an antivirus installed.
The main reason Chrome used to rock was because it exploited a bug in Windows that made it run way faster than any other browser. Since then the said bug has been fixed by Microsoft and Chrome is no longer any better than its counterparts.