North, West or South

[PeterW]

.... That's the intake and extract vents I'm talking about !

I have the option to put both on the same wall around a metre apart and it's a north or south wall, or if I want them further apart it's a west facing wall which is onto a road (but hardly used)

 

I know the general consensus is to have them on the same face - would it matter if I made one a wall vent and the other a roof vent ..? Roof is 50 pitch for reference. 

And which goes where ..??!