Well, these shafts are the two most popular iron shaft.

I myself prefer the sleeker look and slightly higher launch of the Rifles, but if your Dynamic Golds have Sensicore, then you certainly can't ignore their vibration damping effects.

I'd say that if the guy making them for you is Rifle Certified (or at the very least understands how to use the freqcalc.jar program at the Rifle website), go Rifle. It's much easier (IMO) to get a flex more suited to your game in Rifles.