I can only speak to EWR 737 FO vs A320. I choose 737 because it's a much larger base in Newark, and I'm slightly more senior (~5%)- between those two factors I think I am much more likely to have PBS build me a bid group with whatever needs I have that month.

Another factor is that it seems the Airbus out of Newark has a lot of trips with 3 leg days, which I can't stand.

Airbus probably nicer work environment, agreed, but being able to be a part of family life with kids is much more important right now.

Probably all L-UA captains on A320, pretty good mix on 737 but probably more L-CAL. Doesn't make a difference to me which legacy group I fly with, so I can't imagine it would to a new hire either. Good guys and weirdos from each old airline.

Earplugs help a lot on the 737. I bet training is better on A320. Can't be any worse than the 737 program.