I'll keep it simple. Let's say that you have equivalent wheelsets inball respect, except one is .5lb lighter (226g). You weigh 165lb, your complete bike is 15 lb. During sustained climbing, at speeds below which aerodynamics come into play, the heavier system is .28% slower.

But aero effects come into play a little earlier than you think. More like 12 mph. And, of course, you're not only riding uphill at slow climbing speeds, and so an aerodynamic wheel which offers a performance gain of .3% or better is something to consider.

I'd consider Boyd's new 44mm offering and see if he'd do it as 20spoke front and 28rear.