I ended up going with a 3 cross pattern for both wheels. It seems like people think that there isn't much advantage to a 4 cross pattern. Furthermore, the heads of spokes could overlap in a 4 cross, and thus make changing a broken spoke more complicated. Not to mention that I'm not sure whether the Shimano 105 hubs have a high enough flange for a 4 cross pattern.

Thanks for all of the input. What would I do without this forum?