I don't know much about Shanghai Airlines but Skymark is definitely not the same as the ANA companies, conditions and pay at Skymark leave a lot to be desired according to three of their F/O's that where recently hired by Air Japan. If it was an opportunity with ANA I would agree with EK and tell you to come to Japan in a heartbeat but Skymark? I would do some more research about Shanghai Airlines and ask about the possibility of upgrade with both those companies
Good luck