It used to be that the AI version held more advantage but, as has been mentioned, newer powders and bullet designs have allowed the plain old 30-30 to keep up just fine. That being said, I prefer the 30-30 AI. The extra bit of case capacity allows slower powder loads to push more velocity at Contender-friendly pressure levels. Brass life is nearly unlimited plus there's just a certain cool factor in the shape of the AI round. :)
I think if I were looking for a factory barrel I'd be happy with 30-30 but ordering custom, there'd be no reason not to get the AI. Factory ammo can be shot in the AI chamber and fire-forming loads with standard brass can easily be used for hunting and target work.