They both log some data that isn’t user identifiable, which is need for statistics.
The more feature rich platform that AdGuard offers has a larger attack surface, and they have been compromised before, which resulted in user credentials being exposed.
Quad9’s more simple approach is more secure for anyone who just needs a DNS.
Does Adguard block the same trackers that an extension like Privacy Badger blocks? If so, then I don’t need it, I’ll just stick to Quad9 instead.
I would just use uBlock.
I don’t think there is any way around using an ad blocker in the browser, it’s the only way to disable in-page block filters. If you are running uBo there is no need to use AdGuard or Privacy Badger, they all pretty much do the same thing.
The only real argument I see for using AdGuard is that it protects smart devices that can’t use browser extensions, so if you have a lot of smart devices or IOT devices, it might still be a good idea to use AdGuard even if you are running uBo in the browser.
I plan to give this a whirl on a local Pi.