Robert, I run a 1037 stack wagon.  As has been mentioned, the pull type stacker's limitation is hauling distances, you start eating up time in a hurry. If you have nice flat fields with long rows you will like the stacker better than if you have small, irregular shaped, hilly fields.  What happens is this:  the baler turns a corner and a bale comes out and falls over. This may not seem like a big deal untill your off the tractor a couple times a load setting bales up. Or on a steep hillside it can be a problem keeping bales upright.  Heavy, tight bales work best.  I try to keep my bales as light as I can to suite the local market (45-50lbs grass hay) and it causes me trouble with the stacker and the stack,  soft bales squish and your stack falls over. Another issue if you have really heavy hay can be that the stacker almost needs to come right behind the baler at least till a field gets opened up just so the baler can manuver without having bales in the way.  One more thing, running a stack wagon is not as simple as it may appear, it takes some time to learn the tricks of how to operate it.  In other words, you will not be able to have just anyone run the stacker. 

     If I were in your shoes, I would first find out if 3x3 bales were an option with my customers.  Baling speed as well as hauling, storage and loadout efficiency make the 3x3 a really nice way to make hay.  If this is not an option I see the Kuhns system or the stack wagon as both being decent systems.  Which one you choose would depend on your situation.  If you call Kuhns they will send you a DVD of thier system at work.