Great question...a lot of people struggle with this one...and many end up chasing a job with the highest pay...which usually doesn't end up working out all that well.
While getting a large paycheck can be nice, if that's the only reason you take a job, where you aren't very excited about the work you're doing...it will probably be very hard to get motivated every day and the hours will drag on at the office.
If you choose to pursue work that interests you, first and foremost (which may result in less pay initially), your enthusiasm will help you be more successful in the field, which in turn will help you make more money...though it may take some time.
To the second part of your comment, about pursuing a job based on the number of hours required, I'd go back again to encouraging you to focus on finding work that excites you...then you really won't be as focused on how many hours are required.
Good luck to you!
Hope this helps.