Nick,
I am a little surprised that you're now singing the praises of the 48RE. I could have sworn I read a thread of yours titled "shoulda bought a six-speed". Anyway, your entitled to change your mind. As far as I remember, you intend on drag-racing your truck and my advice to you in that other thread was to keep your 48RE. I, on the other hand, use my truck to haul my camper and tow my dirtbike trailer. I'm not interested in racing my truck (I DO race my bike, though!), nor am I interested in modifying my truck to any substantial degree during the warranty period. For my purposes the NV5600 was a clear winner - no real decision required. Both trannies have advantages depending on useage. My advice to anyone buying a truck is to think about how you will use it, both now and in the foreseeable future.
Cheers,
Dave