We have flown out of Atlantic City airport a few times. Very easy airport!! Unfortunately, the airline is Spirit, which has some issues, as numerous people on this board have reported!
I have flown out of Philly and I like that airport, too! We use offsite parking at Winner and have always had a good experience.
Atlantic City is almost 2 hours away, PHL is 1.5 hours away. Our closest airport is Newark (45 minutes). Usually flights out of Newark are a lot more $$ than the other two airports, so the extra drive has been worth it. This trip, we are flying Jet Blue out of Newark and will be using offsite parking.
I would only ever consider using Spirit airlines if there was a HUGE price difference. As long as everything goes smoothly, Spirit is fine. When problems arise, Spirit's lack of customer service can rear it's ugly head.