Pihole and uBlock Origin have different purposes. Pihole blocks ad domains network-wide. uBlock Origin can remove specific elements from specific webpages with surgical precision regardless of the domain the content is served from, so it is a much more precise wide-spectrum content blocker.
In other words, uBlock Origin can block basically everything, but only works in your browser. Pihole blocks fewer things and less precisely but works for all your devices.
Pihole and uBlock Origin have different purposes. Pihole blocks ad domains network-wide. uBlock Origin can remove specific elements from specific webpages with surgical precision regardless of the domain the content is served from, so it is a much more precise wide-spectrum content blocker.
In other words, uBlock Origin can block basically everything, but only works in your browser. Pihole blocks fewer things and less precisely but works for all your devices.