No, it doesn’t. This is just technically incorrect. It’s already hard to compare/analyze two situations on a same hardware. Adding a second layer hardware with variables to it just cannot provide an accurate input.
or may be you didn’t put it to fullscreen (engine.enterFullscreen()
and you have still had the bar of the browser (of a different size between browsers ) or you didn’t fix the camera to ensure you have the exact same view or you captured only a selected portion of the screen 
I’m happy to hear that 
… and I’m sure the Team will be too 
Well, yes. I suppose it is. It will never be 100%. But I suppose you could adjust using the levels (i.e. baseTexture.level or albedoTexture.level or diffuseTexture.level or emissiveTexture.level or if using just the colors then the *color.level). Adjusting the level without changing the lighting would be my attempt. I actually did this in one of my latest scenes 
)
Honestly, there’s I believe better than ‘fresnel’ to create ‘crystals’ fx. Problem is right now, I need to go make dinner… but if you’re still at it tomorrow, I can push you a few links to investigate (or else, make a search in the forum with diamond. There are shaders, node materials and GLSL examples available you can soak-up, twist and tweak to your liking 
Yes. Thank you. I don’t think we can push this a lot further. From the screenshots you provided (and despite the fact that they are not of the same size ) I quickly did this overlay preview of chrome VS firefox. You can see that the difference remains (in my opinion) ‘acceptable’.
No worries. Always happy to help (if I can ) 
Meanwhile, have a great day 