speed wise case with 2x4 or 1x8 gpu's

[intertan]

I am currently looking into a multi case setup, got some hardware lying around and some free time.

Now speed wise if I have 1 setup with 8-1080's  vs 2 setups with 4-1080's would the 4-180;s be faster?
gpu specs are identical regardless if there is 4x2 or 8