I've flown both, and assuming I was going to be stuck commuting for either anyhow, I'd go for the bus. Schedules come and go, but the bus is simply less fatiguing to operate. Easier to fly, roomier, quieter, all that equals less fatigue. In my relatively short experience, for just fatigue level I'd equate 3 hrs in the 737 to 5-6 hrs in the 320. After 2-3 hrs in the 737 I'm feeling the pain. In the 320 the same mildly uncomfortable vibe happened at the 4-5 hr point.

They both fly about the same, just everything is easier in the 320. What is an electrically powered seat worth? After wearing my nice new watch in the 320 with no problems for over a year, I scratched the crap out of it the first week flying the 737 and switched back to my $20 casio after that. Multiply that times 20 minor annoyances between the two. I wouldn't commute to fly the 320 if I could live in base and fly the 737, but at the same base I'd be hard pressed to choose the 737.