Working nights does sound like it may not be the healthiest choice...I understood what you meant about changing positions rather than jobs (sorry my wording wasn't very clear) - I think one of the reasons it is hard to give you pros and cons (beyond saying that working days is probably better for the BP) is that we're not exactly aware of all the circumstances of either position. That being said, some of the things I would consider are how well you feel you would get along with your coworkers in either position (I'm not sure I understood correctly, but switching wouldn't mean you would have to go back to the "bullying" you had to deal with earlier, I hope) - I know you said you feel your current coworkers are lazy and slow so then switching may work out better for you there....One of the cons I can think of is if you have to learn new skills in your new position there may be a period of adjustment/additional stress on you. If you're already fully trained etc. this may not be a problem either.

I wish you luck with whatever you decide!