I strongly recommend Roberts accommodation due to much different reasons. The most important things why you should stand at Roberts place is, because it's close to city center and just on the other side of the street is the metro. Everything was clean and tidy. You could spend some relaxing moments after a sightseeing trip in the Jacuzzi or in the sauna.
So all in all if you not stay at Roberts place you will definitely miss a great thing in Prag.