When I was on the 767 and 777, the FO's said 737 captain wasn't worth the pay. They got very little more, but lost days off. No one mentioned the work rules. Our contract and work rules apply to all aircraft. I'm not saying the work rules are good, I'm saying the senior FO's don't want to give up days off for a small payraise. Some hate domestic flying. Some hate the 737. To each his own.