More ratios + OD sounds like a winner to me, especially if 1st is a deeper ratio; then you have pretty much a gear for every occasion. Not that you need to spin a 512; so the OD is probably of more value than a deep 1st gear.
4L80s are probably smaller, and from what I've read any of the OD automatics, even the Mopar version, are going to require some floor or crossmember surgery, or both.
Nice things about a GV OD unit are easier installation and being bulletproof (at least in my experience in my Dually - 24 years & still excellent).