For your needs, as aaupgrade stated, the Marriott sounds like the better of the two properties. You might also want to consider the Prague Sheraton, which is in the New City, with easy walking access to the Old City. Last time I was there, it was much less expensive than the other two. They gave me a two story suite with a little balcony, there is a lounge and the included breakfast was good. You also do not mention what bars you want to be near, but it's closer to the places I go.
BTW, the FS hasn't given me any UGs in three stays.
Finally, just to throw this out...Uber to the airport is a third the price of anything else. It was my Czech friend's first Uber ride. He is now a convert.