Improved low light performance and a host of other new features but you should probably wait for the new GoPro
DJI Osmo Action 4 sports action video camera launches at $399 - Gizmochina
DJI Osmo Action 4 camera Lights Up w/ Massive New Sensor - Bikerumor
DJI Osmo Action In-Depth Review, DJI's Action Camera
DJI Osmo Action 4 Review
DJI Osmo Action 4 Action Camra - Adventure Combo
DJI Osmo Action 4 Review
DJI Osmo Action 4 sports action video camera launches at $399 - Gizmochina
MY DJI Action 4 Night Settings (Crazy Stabilized)
DJI Osmo Action 3 Review: Cheaper and Nearly as Good as a GoPro
DJI Osmo Action 4: Impressive Upgrades for Low-Light Imaging
DJI Osmo Action 4 Standard Combo - JB Hi-Fi