I think if you went with dual 4.70 gears you would regret it because you wouldn't have the stock low range.  Try it out by not using the stock low range for a while and see if you miss it.  Only use the 4.7 and 4.7 x 2.28 and see how happy you are.  Going 5.0 vs. 4.7 would be a waste.  The 5.0 is actually rounded up so it's less than a .3 difference.  You'll get that by airing down your tires.

I read about one guy with dual 4.70s and he wheeled in low low 3rd which is about low low first in the dual ultimate.  In Moab I often have to gear up a bit with 2.28, 4.70, 4.88 and 35's because a little momentum is required for a climb.  Low Low 2nd or 4.70 1st are the great options from my experience and 4.70 1st is the golden gear if you need a little bump.