My daughter and I stayed at the Bristol Hotel the night before we flew home (USA). It was a large(er) room and very clean. The beds were quite comfortable and we had a very good nights rest before leaving. We will stay there again next time we are in Frankfurt and we will recommend it to friends.
Located very close to a huge railroad station, but not one of the best districts in Frankfurt. Underground parking was available for 15E per night. Easy to walk to a nice pedestrian walk and breakfast at the hotel was great.
I was looking for a Hotel in Frankfurt for a long week-end. Many of the reviews on line expressed concern about safety near the main railway station so I looked for one a little away from the centre. Some were too far outside the tourist area. I had not thought about an apartment but it was very competitively priced compared to the hotels.