Why contrast and lots of image effects dosen't looks good in linear mood?

[ksam2]

I can’t set contrast effect in the Linear mood correctly. I don’t why but all of Image effects work better with gamma

I would like to know Is there a big difference between Linear and Gamma in PBR?
If the difference isn’t too much I can stick with gamma because it works better with Image effects

[Roni92]

The difference is what you see on the screen.