There are a number of variables (all are interactive) and affect both lateral and radial stiffness to varying degrees. So its hard to give a definitive answer.
Might pay to read through the link Kenif posted earlier:
http://www.slowtwitch.com/Tech/Debunking_Wheel_Stiffness_3449.html
Personally I'd go with the builders recommendation. Not sure why you are so set on a particular lace pattern but all things being equal, there is bugger all weight difference, visually as well.
I've noticed no apparent lateral difference between 2 and 3 cross on road wheels (for 32 or 36 spoke counts) or BMX race wheels (32 spoke).
My wheel building bible (Professional Guide to Wheelbuiding by Roger Musson) states:" ...use a standard lacing pattern (2 cross, 3 cross, 4 cross) and the decision which to use is based solely on the number of spokes in the wheel."
Might be worth contacting Duckmeister on this forum, he has has experience in the wheel building industry.