Bug Report
The converter doubles the radius of the VRayLight Disc type. Went from 35 to 70.
Test
I created a light test scene today. It has 1 disc light with 100 radius and 2.12 intensity, and a 50% grey wall 1m away from the light.
Both V-Rays "Default (image)" and Coronas "Default: W" has the same intensity of 2.1 float. So they are 100% identical.
It is the "Directionality" option that is messing with the final intensity.
0.9 V-Ray directionality, 100 radius and 2.12 intensity will give us 0.98 float in the center. To get the same result with Corona you have to use around 0.638 directionality. The converters logit curve converted it to 0.719.
0.8 V-Ray is around 0.54 in Corona. Converter said 0.63863.
Looks like you get better results by taking the logit curve value and subtract 0.1 from it.
So don't mess with the light intensity guys, adjust the directionality.
Lumen
100 radius and 100 lumen in V-Ray is 2.12 Default (Image)
100 radius and 2.12 Default (W) in Corona is the same as 2.12 Default (Image) in v-ray, but it is 140 Corona lumen.
So if you are using lumen in V-Ray and need to Convert your scene, either select Default (Image) before you convert the scene, and change back to lumen when the scene is converted. Or multiply your v-ray lumen with 1.4 to get correct corona lumen.
Sum up
V-Ray Default (Image) = Corona Default (W)
V-Ray Lumen * 1.4 = Corona Lumen
Don't adjust Default: W, adjust Directionality.
V-Ray Directionality = logit sum - 0.1