This doesn’t really match up with my experience for either, can you share something we can look at here? In my view AgX is a significant improvement on ACES Filmic, with the caveat that, yes, you may want to bump the contrast. Blender has 8–10 different AgX looks… have you tried some of these for the scenes in question?
Other goals for a default tone mapper you may want to consider:
- ability to color match to/from DCC tools
- preserve enough information for later color grading
- ability to produce output colors anywhere in the sRGB gamut
I believe AgX Filmic is better for both (1) and (2)… (3) is a debatable goal (I have mixed feelings about this) but the “Commerce” tone mapper recently added to modelviewer is an interesting solution focused on that goal.