Response value difference?

[ajuk3d]

What is the difference between the values for camera imager > response: gamma 2.2 vs. sRGB?

When toggling between them I can see a slight exposure change in the live viewer on my render. What I don't understand is that I thought gamma 2.2 meant the same thing as sRGB, until suddenly I discover these are two separate options in camera imager > response.

Also which option should I choose for linear compositing in Nuke when I render my EXRs?

Thanks.