I've had both in the past, there are pros and cons to each. I think the Ridge Grapplers do a bit better in the mud than the Duratracs, they both handled snow and ice comparably, the Duratracs were definitely quieter throughout the duration of their life. Both tires love to hold onto rocks and pebbles only to later eject them at high speed on the highway, but that just goes with the territory with these tire types.
Personally, I would spend the money on another upgrade instead and ride out the factory Duratracs, you can always buy Nittos for your next set. My 2 cents...