Nice location & nice rooms
This Marriott has been the "go to" property for most of my friends and colleagues. 
Let's start with location - the hotel is centrally located to most of the tourist destinations that you want to go to. It's right next to The Reading Terminal, seriously just a few steps away. The lobby is pretty large, there's a lounge area downstairs, a restaurant that has decent food, fedex & starbucks all in the lobby of the hotel. The staff is super nice & will definitely go out of their way to help make you feel at home. 
The rooms (I've only stayed in a King room) are pretty spacious & clean. The beds are super comfy as are the pillows. Stop by the concierge lounge for refreshments if you have access. They generally have a decent spread of desserts in the evening, also a decent breakfast in the morning. For such a big property, it's pretty calm and quiet once you get up to your room as most of the folks in the hotel are business travelers.