I stayed in Crystal City and have been in a PHL pad now for about 6 months. I wouldn't choose one over the other strictly for pad purposes. Nothing wrong with Philly, in fact I prefer the pad up there to the ones in Crystal City. Those are small cramped and in an expensive part of town. The pad I'm in in Essington is a house, central A/C, mostly newly renovated, very quiet part of the town outside the airplane noise. I go running and biking back behind the airport/UPS/tower when up there. It's very safe.

PHL pads are $3.60 round trip by bus that runs about every 20 mins during the day and 45 mins at night. It's predictable and schedules are known. Once on the bus, assuming you're going to Essington, it's about an 8 min ride. Super quick.

I walked from DCA in the summers and winters and it was miserable. Cabs are around $8 though, so if it's raining that is always an option.

I admit I had a bias against PHL before I got here. I was very nervous about the pad situation, but found it to not be warranted.