Thanks for these comments.
I'm still undecided.
Though //// looks better my original thought was \/\/ giving four pairs of like corner pieces and a chance of getting them wrong. I solve top corners first and would have to think about the bottom corners to see if the were all positioned correctly. With //// there is a possibility of getting the side colours in the wrong sequence because the colours aren't linked - but in practice with a RWB (BOY) colour scheme this wouldn't happen. Either way I want the orientation of the top to bottom pieces to be important.
I've stopped here till tomorrow with top white and bottom yellow.