I'm a plumbing contractor and have been using battery tools in my company since they came available. I do know that the two dewalt batteries you've mentioned ARE interchangable. I believe I saw recently at a Home Depot that dewalt has come out with a 2 pack of batteries for 89.95. I don't know if it's going to be permanent or just a temporary special. As far as the tools themselves go, I prefer Ridgid only because they have a lifetime warranty on the tools and lifetime replacement on the batteries. In my company, I have some trucks with Dewalt, some with Ridgid, some with Hitachi, Milwakee, and some with ryobi. As for durability, the Hitachi and ryobi are about the same. Once they wear out we just throw them away and replace them. The Milwakee seem to be the best but most expensive followed by Dewalt. Just my .02
To heck with work, lets go fishing.