Maya 2020 / Vray Next - slower than Maya 2019

[chronopsis]

Having some weirdness in using Vray Next with Maya 202 vs Maya 2019. Vray in Maya 2020 is noticeably slower. Made a few tests with both GPU and CPU rendering. Tried reinstalling Vray but made no difference.

In the screencaps below you can see that in 2020 the initial rendering steps:

"Preparing scene for rendering"
"Preparing Scene for frame"
"Compiling Geometry"
"Building static raycast accelerator"
"Building GPU dynamic nodes"

...which in 2019 go by so fast they aren't even apparent, take up the bulk of the rendering time increase.

Wondering if there is some setting in Maya 2020 Vray that I've forgotten about.

Maya 2019, Vray Next GPU

Maya 2020, Vray Next GPU

Maya 2019, Vray Next CPU

Maya 2020, Vray Next CPU

[yolov]

That sounds very weird. There is no difference to the V-Ray code for 2019 or 2020 that could cause this.
What 2020 point-version is this? There may be something in Maya that was fixed with a point-release (I think the latest is 2020.4).

Also - is this for every scene, or just this one? Are there any caches enabled for V-Ray in one session, that are turned off in the other (Render Settings > Overrides > Rendering > Cache geometry / cache bitmaps)?

Are both Mayas set to the same animation evaluation mode? There are some differences between DG and Parallel/Serial evaluation in terms of export from Maya.