Safari ad blocker extensions will never be as powerful as uBlock Origin in terms of the sheer number or types of content they can block, but they can be as performant or efficient, or even more so. To my knowledge, uBlock Origin uses its own custom networking engine through webRequest, WebShield uses Safari's content blocking API which is baked into WebKit. When loading a content blocker in Safari (& thus WebKit) rules are converted into DFA in WebKit [0]. Pretty sure this is the code in WebKit [1]. Yes, the content blocking API is more limited than full blown adblock filter list syntax, meaning its not as powerful, but it is more performant & efficient than uBlock Origin, within the subset of rules that it supports. To complement the content blocking API we use scriptlet/extended css/css/js injection in advanced blocking, similar to AdGuard. The AdGuard guys probably know way more about the specifics of how content blocking works in WebKit than I do though. But I do know that the content blocking API in WebKit & Safari is more performant/efficient than uBlock Origin, subject to limitations on powerfulness in terms of the types and number of content that can be blocked as mentioned before.

I still feel like I need to performance test WebShield more to back my claims, so take it with a grain of salt, but based on what I've seen, it is comparable with or better than uBlock Origin in terms of performance/efficiency, not pure power, but again, please take it with a grain of salt, because I can't believe it.

[0]: https://en.wikipedia.org/wiki/Deterministic_finite_automaton [1]: https://github.com/WebKit/WebKit/tree/04edf7716a74170fb0967f...