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.
I have the Dyad's in a 700c and they're bomb-proof. I can't really give you a comparison opinion because I don't know the other Velocity rims that you mention. Another great rim in a 700c is Salsa Delgado-X.
There's plenty of 40 hole hubs out there. Phil Wood, Chris King, White Industries, to name a few.
that's a little funny. i bet shimano makes more hubs in a day than those 3 manufacturers combined in a year. Plenty?
i assume folks have a budget in mind when they are asking for ideas or comments. the OP indicated he was using a 105 hub, so i quickly checked for availabilty of 105 xt and lx hubs in 40h 130mm or 135mm (sometimes you can fit em). and there aren't any that i saw listed. i suspect shimano doesnt even make them.
not many folks are willing to spend $500 for a hubset.
i have some "fancy" sealed bearing dt hubs that i got from ebay for $110, but i question whether they are ideally suited for touring due to the poor availability of replacement parts. Few bike shops outside urban areas stock any parts other than shimano. in fact 105 / lx level would be fancy stuff for rural shops.
then again new hubs probably won't give you any trouble for several 1000 miles provided you don't get heavy rain or submerge hubs.
A velocity aerohead OC is far too light for loaded touring and it has very shallow braking surfaces.EDIT: OK the OC side in the pics looks wide but the other side is very shallow beleive me. I'm considering using them as a lightweight road racing rim but I don't like its shallow braking surface so I will probably go with a Mavic rim. Anyway rims of the Aeroheads width are only used for tires up to 28c. Is that all you intend to use?
You can now get the Velocity Synergy OC is 700c and this rim looks ideal to me. Its light for a touring rim but still looks reasonably solid and it would work well with 32-35c tires.
See, http://velocityusa.com/rim-diagrams.php EDIT: OK I should have looked at the drillings first as there only listed as 32 hole. You could always contact velocity through a dealer. Aparently they do special orders every now and then when they have enough to do.
I agree with Anthony about the 700c Synergy OC...it is lighter than the A719 wheels that I have but is very sturdy and stiff for lightly loaded duty. Loaded touring, I still use A719 rims but I am rather large. The Synergy OC is really nice with a 25-32 tire on it!