Not sure if anyone is still interested in this. If not, let me know.
Below I rendered a test with gray materials. I removed the glass. No DOF still.
I did Fstorm, Corona with cache and Corona brute force.
Corona with PT never cleared the noise, even after over 300 passes.
It seems that Corona with path tracing is closer to Fstorm in terms of depth of shadows than with cache. Probably expected though.
So may be if we want more depth like with fstorm we need to use path tracing exclusively.
Look at the shadows inside the profile:
With cache, the shadow inside that tube is not as defined as with brute force and fstorm. I believe this is in part why people think tone mapping is the problem. Because we try to get more contrast but there's just not enough detail to begin with.
Corona Cache:
Corona Path Tracing:
Fstorm: