Start by identifying your main use—underwater photography, rugged adventure filming, or casual vlogging on the go. Then compare form factor, stabilization type, water protection, battery life, storage needs, and accessory compatibility. For underwater work, look for rugged housing options and an appropriate IP rating; for portable daily use, prioritize a compact, lightweight design with solid stabilization and easy mounting. Consider whether you need a built-in gimbal (mechanical stabilization) or advanced electronic stabilization for 4K video; DJI Osmo Action and DJI Osmo Pocket each suit different scenarios.