Tugs vs osv as far as pay

hey guys I’m just an OS right now have enough sea time for ab osv and kind of wanted to try crew boats or supply boats but few ppl say they pay less. Anyone know if the pay is that great of difference. like 60 more days will have enough time try get my ab special if you get ab special do you get more then ab osv if you work on supply boats? Just if anyone knows range AB Osv gets paid or AB special for supply boats i would appreciate it thanks