Fob bus stop puts you closer to NEC, Boltbus will put you off next to the regional rail which you could take to the airport, but thats about $7 one-way and you'd have to wait for the shuttle to the hotel. They are both the same price, its just that Boltbus needs to be reserved in advance and if you miss your time, you aren't guaranteed a spot in any of the next buses(not to add that you dont know when the next bus will come lol)
So both $20 roundtrip, Boltbus you pay for online and commit to your time, free wifi. Fob bus, you walk up to the bus and get on whichever one comes first, buses arrive every 30 mins, if you miss your bus it doesnt matter because the tickets arent confined to a certain time(you just use it whenever you feel like getting on a bus)
Have $3 for transportation once you get into philly