QOL decent at Atlas, career kind of company?
No...and Yes.
It depends on what you want...ACMI vs. scheduled carrier.
See the world right away, with a relatively quick upgrade to captain (Atlas), or make more money and have more security (probably) (DAL/AA/UAL).
Want to be home every third or fourth day (Big 3), or be home in large blocks of days (Atlas). Atlas you can be gone 30 days, if you want, and I know two guys who had, basically, 60 days off in a row.
Have a schedule set in (almost) stone (Big 3), be willing to have your schedule change massively, on sometimes on an hourly basis (Atlas).
Go to a lot of domestic locations, and, when your seniority allows, a few overseas destinations (Big 3), go to places like Kyrgyz Republic, Georgia, Azerbaijan, Romania, Cape Verde, Republic of the Congo (French Congo), Russia, Iceland, Malta, Sri Lanka, Indonesia, India, Paraguay, Brasil, Chile, Ecuador, UAE, Saudi, Bahrain, Angola, Singapore, Spain, Zhengzho, Shanghai, Hong Kong, Sydney, Melbourne, Narita, Nagoya, Incheon (Atlas). I have been to all of these in the last 4 years...some of them, like HKG and SYD (Coogee Beach) a LOT of times.
I think for an "normal" pilot, DAL is best (unless you live in AK/West Coast or HI..then Alaska or HI is best). I think for an adventurous sort, Atlas is best.
Sorry...forgot SWA...they are really good, also.
And, it REALLY varies between individual. Talked to a guy who wants to go to JetBlue...it's his ONLY choice. He lives near Boston and wants a Boston base...he will not be applying anywhere else, unless they open a BOS base.