It appears that uBlock Origin is still the way to go as it has been for a while.
During my testing, the built-in ad blocker was not only noticeably slower but also blocked content that it should not block forcing you to white list sites for no reason.
The mainstream extensions do not cause you such headaches while offering additional features like subscribing to different filters. I doubt any extensions will be able to use less CPU than a built-in ad blocker, but it simply is not quite there yet to be considered a full replacement in my opinion.