Those RF trannys are related. I wouldn't get caught up in 5-spd or 6-spd or 8-spd. I have vehicles which have 4, 5 and 6 speed tranny's. They all work ok. Yer not going to get 100mpg with any of them. Yer talking shades of gray in economy, which are easily mitigated by your driving style. If it's economy you're worried about you probably should be looking at a small car. I'm pretty sure all the 2012 Ram RF's were 6-spds, or the ones I've seen were.
What people don't always point out, is the more gears ya have the (often) more lag there is when you go to pass someone ...dead-spot during downshifting in many cases. Deadspots reduce spirited driving. On our older Jeep GC with a 5-spd V8, on the hwy, it almost never needs to downshift to pass. Put yer foot down, Boom! it goes RIGHT NOW ....the power is right there right now, and yer around that slow turkey before they knew what even happened!! he he. None of this slow 'wind-up' ..down shifting to get into the powerband to get up to speed, like someone's grabbed yer truck by the scruff and it's waiting for things to 'kick in'. And frankly, that can be one issue on the Rams when they're in the MDS (Economy) mode. You want to pass, there's a lag to come out of that mode and then find the 'right' tranny gear. Things fall flat in that 2 seconds.
Trannys with a lot of gears that are shifting all over the place up and down every start and stop, hill and noll ....might eek out another mpg or two, but can be awful to drive day in and day out. I like the gear-select toggle on the shifter that allows me to limit the top gear for times I'm not going real fast or on hills ....don't need to be shifting into the top gear or going into 6 or 4 cylinder mode.
You'll have to drive both trucks and see which one drives the way you like it the most. Pay attention to the lag and shifting like I described above. One may suit your driving expectations more than the other.
