[Dah00n]

>Having a third party monitor

If you install an extension that shares your browsing habits then that is on you of course but good ad-blocking extensions doesn't do that and if the data doesn't leave the extension it isn't really monitoring you. I would personally trust the author of uBlock Origin and the in-built uBO made lists over Safari and Chrome any day. Both Apple and Google are running advertisement services so I don't see any reason to ever put any trust in them doing what is best for the user in blocking ads. I wouldn't really trust Mozilla that much either come to think of it.

>hundreds of thousands of rules on every page request becomes a significant source of slower page load speed

This is a myth really. Almost all websites the average user visit have some form of advertisement and/or tracking. Such sites load much faster with any good and modern ad-blocker installed. Besides, it is not like any developer worth his salt would run through hundreds of thousands of URLs looking for a match. The only time it does add any overhead is on a site with nothing to block at all and the amount is tiny compared to the time wasted on all the other sites.