Surprised about Tor Browser though - it's basically Firefox ESR with some tweaks with the Tor package bundled (that can be deleted). Performance should have been the same. And since they also prioritise privacy (more than Mozilla) I figured it is a better bet for uBlock Origin - wonder which tweak causes that slight difference between it and Firefox?
Also, what about the new Orion (Beta) browser based on Safari / WebKit? If I remember right, they claimed they had made changes to WebKit to support uBlock Origin better and properly than either Safari or Chrome.
I believe that test was taken after CNAME-based blocking became available in Firefox but before it made its way to Tor browser (which, at least at the time, was based on Firefox ESR). I suspect a modern run of the test would show the browsers as similar.
I wonder if it's something like the default settings of Tor Browser already prevent some ads that uBO also would have blocked, so that just makes the numbers worse for uBO, even if the user isn't seeing any more ads.
Only other theories I can come up with would be Tor Browser interfering with uBO functioning optimally, or its version of FF not being new enough to work optimally with uBO.
Also, what about the new Orion (Beta) browser based on Safari / WebKit? If I remember right, they claimed they had made changes to WebKit to support uBlock Origin better and properly than either Safari or Chrome.