Probably a little extra from ASA especially if you're in a regional tower. If you're in terminal radar or enroute there's probably not much in it. The climb up the pay scale happens quicker at ASA too. The pay jumps are about 10K per year for about 10years compared to airways 3k per year for about 20 years
Both pay just under double time for additional duty.
ASA will give 12.5% super compared to airways 11% (you put in 5.5% and they put in 11%)