Well yeah, RAW... and for bayer-originated images, storing as raw bayer will always be more efficient. Prores is 422 or 444 which wastes 2-3x the space on interpolated luma and color data. Not to mention the flexibility of RAW, RAW development, and non-destructive metadata controls. Prores bakes in debayer algorithm, whitebalance, gamma, etc and takes up 2-3x the space for a more wasteful and less flexible container. It's also generally much easier to do highlight recovery on RAW. That said, for a lot of productions, Prores is just fine and generally an easier and more well adopted workflow as long as the RAW processing and transcoding is done properly.
+1