IF your only driving 12 miles (each way?) for work, I would go for the 4:10's if it came down to 2 trucks with only the gears being different. Is this needed, NO! But what IF you get a bigger trailer down the road? I would have done the same if I had the choice.
Not to mention rumor has it (can't remember where I saw it!) that 4:10's became standard because they will "allegedly" get better mileage than the 3:73's. May be speculation??? Or GM had a ton of 4;10's they needed to move off the shelves!!! Lol
NOW with that said, I am very happy with my '13 -2500 6.0/6spd/3:73 crew cab 4x4! Towed our ~7300lb trailer just fine the one trip taken after we got the new beast! Our one trip was fairly level towing, about 60mi each way. Can't remember the mpg, maybe 9ish??? Only had 1k miles on the truck at the time.
Have also towed our 2 place 12' tilt clamshell snowmobile trailer and got about 10mpg w/ wind. The truck has about 3500 miles now. So still breaking in!
So far loving the beast. Though Mi roads are HORRIBLE right now due to all the heaving from the frost this winter. Worst in years from what I remember!!! One thing I wish the GM trucks had is a "light load" selection for tire pressure like my buddy's Dodge 2500 does!!!
Also, if you get the 20" wheels, there are only 2 tires in the stock size currently available!!! i was told about a month ago by Cooper that their Discover A/T3 will probably be available in our 265/60/20 this Spring!!! I am hoping they don't change their mind!!! Had a seton our '10- 1500 and was very happy with them!