For the simplicity factor, air-to-air FTW!!!! Water to air , IMHO, has too much junk to make it worth it.....I have no first hand experience with them, but my buddy with an 03 cobra has had the resivoir boil over after only one or two runs....that sounds a little too hot and in-efficient to me.
+1...I think for the Hemi water trumps Air to air...you need a much larger intercooler for the same results. We have such hot running engines to begin with i think water to air is the way to go for us. Leaves you more surface area for the radiator to work properly and cools the temps efficiently. If you want things even cooler...spray some water meth