I looked into it, and, while the new singles have a wider stance, the duallies' stance is unchanged. Apparently the seats themselves are narrower. I think both changes are for stability purposes, though I've not seen any complaints about stability on the older ones anyway.
Since the accessory port is the biggest update, you might be better off with the previous generation, because you'll get more bang for your buck. Just in case, though...
The lack of a fold lock might annoy me, but you can just install one yourself. The new one is a buckle on the wrist strap and a lower point on the frame, so it's still not super easy. You might as well just thread a buckle (available at craft and climbing stores) onto the old wrist strap and use that.
Some people complain about the fabric covered "nose" on the stroller (new ones have a plastic guard over the plastic), but I really think that's an aesthetics thing. Fabric looks "worn" more quickly.
Another thing that comes down to preference: the newer one has a thinner handle bar. I think I mostly see this pointed out because people favor the older one, so you're probably okay there.
If you don't see anything here that makes you not want the old style, then I think that would be the best fit and beat deal for you