There were two parts to it: Is the FX9’s raw out as good as the raw from the F5/F55 and then – do I really need raw.
The F5/F55 with either Sony Raw or X-OCN offer great 16 bit linear raw in a Sony MXF package. The files are reasonably compact, especially if you are using the R7 and X-OCN. There are some compatibility issues however and you can’t use the Sony Raw/X-OCN in FCP-X and the implementation in Premier Pro is poor.
The 16 bit out from the FX9/XDCA-FX9 gets converted to 12 bit log raw by the Atomos recorders, currently the only recording options – but in reality you would be extremely hard pushed to really see any difference between 16 bit linear raw and 12 bit log raw from this level of camera.
Personally I feel the reduced noise levels from the FX9 makes footage from the FX9 more malleable than footage from the F5/F55 and if you are shooting in FF6K there is more detail in the recordings, even though they are downsampled to 4K raw. But the FF6K will have more rolling shutter compared to an F55/F5.
I would suggest anyone trying to figure out whether they need raw or not to start by to grading the XAVC-I from the FX9 and see how far you can push that, then compare it to the raw. I think may be surprised by how little difference there is, XAVC-I S-Log3 is highly gradable and if you can’t get the look you want from the XAVC-I raw isn’t going to be significantly different. It’s not that there is anything wrong with raw, not at all. But it does get rather over sold as a miracle format that will transform what you can do. It won’t perform those miracles, but if everything else has been done to the highest possible standards then raw does offer the very best that you can get from these cameras.