I think the auto is the way to go too. 8 speed in 2015 up and that is a big improvement over the nag1 in the older models. Get a paddle shifter if it doesn't already have it. Also, if you buy, make sure it doesn't have any cam/lifter issues. That "hemi tick". If you get one with a 5.7, I recommend upgrading the oil pump to eliminate future lifter/cam issues. This raises the PSI at idle to those areas. I forget if the 6.4 has that issue or not.
It is not the oil pressure at idle causing the lifter failure, they have the same (usually more actually) oil pressure they did in 03-08 and I have never seen one of those go bad. They changed the needle bearings in the roller tip in 2009 when they re-designed the lifter for more lift and they are small needles and shrouded from splash oil. Just like how a shopping buggy wheel is so small it gets stuck on a peanut on the floor a tiny needle gets stopped by a tiny particle and makes the lifter start sliding on the cam instead of rolling on the cam like how a freight train wheel would roll over a peanut. It is a lifter problem and nothing else.
As for the car the original poster is asking about buying I would take the manual hands down any day of the week but it really is a personal preference. Also if I had the money I would get a 6.4, they will smoke a 6.1, they got better heads, better cam, better exhaust, better intake more compression... however if you get a 5.7 then a 6.4 is a bolt in later on down the road.
