nitrous engine question

I am getting ready to change things up in my small block chevy, my question is
what are all the big hitters doing for compression ratios?
I have heard a while back that their lowering the compression allowing more nitrous into the cylinder. but lately I have been hearing of them running higher compression like 14-14.5:1?

motor is a 12* sbc, compression now is 13.5:1
im gonna bore the block out some and order new pistons, what should I go with? and the reasoning for it?

thanks