I'm not trying to dissuade you from your decision but, none of the diesel powered trucks are perfect, right out of the box.
I have a couple of friends with Duramax/Allison's & they are happy with them. However, they have their problems, also.
As well as the Allison shifts, along with extra gearing, I've heard that the new Dodge 48RE's have fewer problems. My one friend is on his second Allison. You are very close to one of the premier, super heavy-duty, transmission shops in North America. DTT (Diesel Transmission Technologies) in Abbottsford, BC (Can. ) can probably upgrade your trans. to bullet-proof status. Since your trans. is so new, it might not be all that expensive & you will end up with one of the strongest transmissions you can get.
Some of the newer Duramaxes are having overheating problems. Don't know if they have a fix for that, yet.
If you get a 4X4, the frame hangs down very low. Any driving on rough back roads may compromise the skid plates. My one friend bends his up almost everytime he drives on rough back roads. He's had to bend it back into shape & sometimes, it's bent up so badly that it has to be replaced. On his last trip, he bent it up so badly that it "tweaked" his frame rails, inwards. He occasionally asks me if he could use my Dodge because it has more ground clearance & as he says, "It's just a little bit tougher".
Don't get me wrong. Neither one of those guys would trade their Duramaxes for my Dodge. They like the quietness, ride & all the "bells & whistles" (electronic gizmo's) on the Chevy's. I, on the other hand, would not trade my Dodge for both of their Chevy's. I don't dislike their trucks, I just LIKE my Dodge/CUMMINS!!! Enough to have two of them.
Generally, the Duramax/Allison's are more expensive than the Dodge/Cummins, also.
If you do decide to go with the Chevy product, I don't believe you will be making a "terrible mistake". The vast majority of Duramax owners, that I have spoken with, really like them. All the trucks have their plusses & minuses. If the Chevy has more plusses & less minuses than the Dodge product then, that's the truck for you.
Check out the Duramax website. I believe it's Diesel Place.com.
Best of luck with your decision.
Joe F. (Buffalo)