the aero is their lightest road rim 21mmx20mm wide, 400g. dyad is 22mmx24mm wide, ~525g. weights from weightweenies.com. mfr lie about weights...
my guess is the dyad is more durable. the asymmetric spoke holes will of course help some. i have built several synergy rims up, theyre ok, ~435g. i have managed to deform / crack out one synergy with too much spoke tension and normal fatigue (this was fairly easy to do on mavic 517s @ 395g).
I have had good luck with mavic 519s, no crack despite high tension, 465g. so my opinion is the more weight (presumably in the spoke bed) the better to allow high tension and prevent loose/broken spokes (which i really never have anymore since i started building my own).
i'd rather have a slightly heavy slower wheel and not have to fuss with wheel problems. this philosophy extends to my tire preferences as well (heavier and wider is better, cushier ride, fewer flats). note i am not advocating crazy heavy downhill weight rims like some folks use (sun rhino lite for example).
a tour is a tour after all, not a race.
even better would be a 40h dyad rim and hub. thats how they used to do it. 40 r 36 f on those jap touring bikes.