From personal experience,
I have owned a gen III non-dod LS, since new, that has Needed Zero (0) maintenance for 50K.
It was eazy to lightly modify for very respectable power, I get great cruising (city or highway) mpg. The idle is pretty stable, power onset & response are as good as anything I've driven. And with no EGR and the back O2 sensors programmed out (for headers, etc) the engine seems to be staying clean and hastle free.
In the interest of full disclosure I will say that I changed the spark plugs once...but that was more of a "why not, I'm already modding and its easy to do with everything already out of the way" type of deal . . . I also run a K&N which seems to get a bit of oil comming off of it after cleanings, so I take the airbox off (30 second job) once in a while and spray some sensor cleaner onto the MAF sensor. (If I did not run an oiled air filter, I don't know if that would still be necessary or not)
I also own a non-VVT Hemi WK that had 40K on it before I bought it. It gets single digit MPGs in town (even with low traffic) and doesn't do too well on the highway at 72, but it does get semi acceptable mileage if I cruise steadily at close to 50 (I'm not sure if that is because of the aerodynamics of the WK that make it a few mpgs worse at 72 than 50 or if its like one tech I talked to "guessed"-he said he wasn't sure, but he thought that the DOD only worked below 60 and after that I was running on all 8, all the time)
My hemi also has worse idle quality, and a studder on acceleration . . . as in, sometimes it takes right off, but often it hesitates. Overall it just isn't smooth at very low speeds. It also appears to need a lot of maintenance, EXPENSIVE EGRs, that problematic little sensor (forget the name right now) at the back, that is a b***h to change, and if the throttle body gets as dirty as it does, now gunked up is the rest of the intake/engine? -> from what I read, those appear to be issues with many hemi's, not just mine.
For me, it seems like a clear choice when picking one V8 or the other . . . but overall my experience is somewhat limited (especially with the hemi) and I know there are other opinions.
So lets hear them, which one do you favor, and why?