Skip the S3 entirely, the Droid DNA has better battery life, processor, screen, and sound quality. The only thing the S3 has is an SD slot but I'd doubt you'd use it. The RAZR Maxx HD is still a better buy than the S3. The way the tech world is, there is always something better just around the corner, so I recommend buying now while you can.
I read reviews saying that Droid DNA has really short battery life due to its powerful processor and high resolution. That it can't even handle 2 hours of light gaming.
And if S3's battery power is even worse than that, @_@.
I guess razr is the way to go.