I experimented with circle hooks this past summer pulliing cutplugs for resident silvers in the sound. My fishing partners fished normal hooks. Same bait. Caught lots of shakers and around a dozen keeper size fish.

Overall, I would say that circles don't hook fish as well as normal hooks (maybe only half as good as normal hooks). That is, not as many of the bites get hooked. But once hooked on circles, fish never came off. I hooked eleven keeper size fish on cirlce hooks, and didn't loose one. With normal hooks we typically loose between 25% and half of all resident silvers after hooking them.

However, later in the season when the fish started to get persnickety and just slashed at the bait, hooking fish with circle hooks was nearly impossible.

I would say that circle hooks are much easier on bigger fish to be released. But, for the really small shakers (under 12") I think the circle hooks are much more damaging.

PS all our fishing was with with 1 and 1/0 gamis either circle or octopus.