As was mentioned, there is a critical difference.
Ducks Unlimited was founded as a habitat improvement organization. If you read their statements, they are about the preservation and restoration of wetlands. They are ok with hunting, they support it, but they are not an organization specifically for duck hunters, except that they were founded by duck hunters and are probably 99% supported by duck hunters.
Delta is a research based org, with the goal of putting more ducks in the air, and supporting duck hunters. They approach from a holistic standpoint - do everything you can to produce more ducks on a given acre...predator control, etc., where DU takes the approach that having more acres will be better for everything and everyone.
Both are right, in their way. Delta takes the idea of working with what we have now, DU wants to acquire, improve, etc. more.
I think DU has really grown beyond their founders' intent, and I think the idea of DU putting improvement money into private clubs sucks, but I'm enough of a realist to know that if I had a club, I'd probably be looking at every dollar of help I could get, too...
As far as spending money north versus south, that's a tough call, and I'm glad I don't have to make it. Which takes precedence? You could put 1,000 acres of nesting habitat back into production right in the heart of duck breeding country, or you could do what in Arkansas? Put more water control structures in Five Oaks? Improve some boat ramps? Buy another public hunting area (which is outside DU's scope)?