I worked a part time job with full time hours.
Benefit:
-You still are considered a part timer, so the expectations aren't as high for you as the full timers.
-The more you work, the better you look in your boss' eyes because you technically don't have to work those hours.
-It's easier to trade shifts because you don't have a required amount of hours like a full timer. So if you do end up not working 40 hours in a week, nothing is held against you.
Detractor:
-No benefits.
-Sometimes its hard to get 40 hours every week. Usually I got 40 hours by exchanging shifts with full timers that didn't want to work 50 hours a week, but sometimes they do, so you don't always get their shifts.
-No holiday pay.
-No sick days.
-Less of a bonus (if the job has them)
Theres probably more, but I can't think of the at the moment.