"Never cross the valve hole, (first lesson told to me, long ago)"
I always build so that the spokes cross at the rim seam. With 32 holes this makes it necessary to cross the valve hole. Crossing the valve hole is just a slight inconvenience, while I feel that crossing the seam is correct and makes for a better build. I also finish true to less than a quarter turn, so I don't concern myself with how the nipple flats are aligned, but I ALWAYS make my rim labels readable from the chainring side.
Kevin