I also went through the decision factors of the Ranch Han Grille Guard vrs the full bumper. I decided on the grille guard because I was concerned more about all the front end weight with the engine, etc that was already there plus the crumple zone considerations then the sagging spring stuff. After I installed the KORE Leveling Kit and the heavier springs I did re-consider getting their bumper but decided the grille guard was good enough when I took out a 250# buck with it at 50mph or so, NO damages to the grille guard or the bumper/fenders etc.
I have seen 2 Dodge trucks that were in accidents, both high speed and almost head on, one with the grille guard and the other with the full bumper. The fellow with the grille guard actually came out much better, basically un-injured. The fellow with the full bumper had a lot more injuries because the front end did not crumple right. That also made a bit of an impression. Both of the other drivers were in smaller cars, they were killed.
Having said all of that, I still really like the looks of the bumpers and easily could be persuaded to get the full bumper.
CD