my 17 ram is a 6.4/3.73 truck. i have a family of 4 and my two sons are over 100lbs each.
even loaded heavy with all of us in the cab and bed loaded with firewood, and my tt around 6k loaded, the truck pulls very hard, even in the hills. so much so when it gets down into 3rd gear, i have to back out of it because i accelerate too much (up the hill) no joke.
to me the 66rfe is fine and shifts way better than the clunky lousy 6 speed my 15 Silverado 1500 had, of course according to gm was normal.
if i was towing north of 10k, I'd hold out for a 4.10 geared truck, but for the 7 or so times per year i tow, at the weights I'm towing, the 3.73s are more than enough.
as said,, all 3 make a good truck, I'd own any of the big 3s HD trucks