If you are all about 3G now, the DNA may not be the phone for you. The DNA will be great once you get LTE in your area, but, if you are going to pay full price, I think you would be better off sticking with the Rezound, and, waiting until there is a phone that you have no reservations about buying.
As for future upgrades of the DNA vs. the Maxx. the Maxx is running on an older processor, vs. the DNA, which is running the "latest and greatest" processor. The DNA has the same chipset as the Nexus 4, so, you could imagine that the DNA should get at least one update.