Here is a comparison review of the Sony FX3 vs Sony a7S III full frame cine cameras. This comes from DPReview TV. They’ve published their Sony FX3 review and compared it to the Sony a7S III. You can check out the video and find out which one you should choose.
The Sony FX3 is Sony’s most compact and lightweight Cinema Line camera that is ideal for handheld shooting, gimbal and drone-mounted work, and it bridges the gap between the portability of the a7S III and the capability of the FX6.