I have stayed at the Pen, MO, FS and Ritz. Without doubt, for me the Peninsula Tokyo is my favourite ( or BEST ) hotel in Tokyo ( and 2nd on my all time list ). I actually have a rather complete collection of photos of the Peninsula Tokyo in my flickr site. You may want to take a look to help your decision.

http://www.flickr.com/photos/benlee1...7602495394952/

And also for the other hotels :

Ritz Tokyo : http://www.flickr.com/photos/benlee1...7602439310966/

The Four Seasons Marunouchi : http://www.flickr.com/photos/benlee1...7607554322689/

And lastly, the MO Tokyo ( not recommend ) : http://www.flickr.com/photos/benlee1...7607903452351/


Hope it helps. Have a great trip!