GoPro - HERO12 Black vs DJI - Osmo Action 4

These two are evenly matched on the broad strokes, with the decision sitting on which individual spec advantages weigh more for your use.

Pick the HERO12 Black if you care most about max video. The biggest gaps in its favor are max video.

Pick the Osmo Action 4 if you care most about waterproof depth and stabilization. Its strongest claims are waterproof depth, stabilization.

Both ship with comparable max 4k fps, horizon lock, so those specs don't separate the two — focus on the differences below.

Bottom line: there is no wrong answer here — match the spec advantages to how you actually use the product. The Mars Score parity tells you both are well-rounded; the differences are about trade-offs, not quality.