The “blocks more ads” part is probably mostly because AdGuard allows you to add the “normal” blocklists that you find all around the Internet (plus it has a large collection of built-in ones already).

IIRC 1Blocker uses its own format, which isn’t as prevalent.

I use AdGuard. Used it for years - with brief stints of 1Blocker - and I feel like AdGuard blocks more ads and breaks less sites.