Pay-wise, I made more as a new grad in psych than I would have made in med-surg...quite a bit more. It depends on the facility.
I also started in evening shift...I like that shift the best. I wish I could work them again, but I can't right now so I have to stick with days.
The pros are that by 1700 administration is out the door so they're not around to bother you. Also, doctors have already seen the patients and any treatment teams/meetings/etc. are all over and done with. You're not fighting to find charts, dealing with labs/pharmacy or carrying out orders. The environment is far more relaxed for patients and staff, at least in my experience. No discharges since they happen on the AM shift; perhaps a couple of admissions. There's only one meal to deal with. By 2100 you're passing out the evening meds, (hopefully) most of which are sleep aids. Most patients are asleep by 2200-2230.
Cons: doctors have already come and gone so if you need to get something for your patient, you'll have to call the doc. There's fewer supervisors on hand, so if there are issues you may have to wait for help depending on how many other fires they need to put out. Staffing may also be skimpier. It's possible that you may be flooded with admissions (some nights it's like they are giving away something for free if patients will check in). If you get a discharge on the evening shift, it's almost guaranteed to be AMA so you need to deal with that too. Also, there's no guarantee that all of your patients will be asleep by 2200; in fact for the night-owl psychotics, the fun is just beginning.