I have not stayed at Keio Plaza, but have stayed at BW two times and I absolutely love the hotel because of its location, price and good rooms. The breakfast has also been more than decent for me as well. Even though, the neighborhood is what it is, I have not ever felt worried walking the streets any time of the night. If you want more relaxed surroundings at night, I guess Keio Plaza would suit you better. Don't expect much of the BW's "Club Lounge", though. It does not offer you beer, wine nor even good coffee. The lounge is equipped with a coffee machine from which you can get hot or cold coffee and few other drinks.