I have tried both Peninsula and MO Toyko and besides the inferior room quality and amenities of the MO when compared to the Pen, the MO's service was really bad during my stay, full of excessively polite but annoyingly incompetent staff that cannot fullfill and understand even the simplest of requests. Perhaps it's a one off bad luck incident but I certainly won't go back to this hotel. On the other hand, I have stayed at Pen Tokyo many times over the years and usually find the service to be fast, competent and exemplary.

One particularly impressive case I can recall while staying at the Pen involved a housekeeping staff that managed to get the hotel electricity technician to unplug and reverse ( turn upside down ) the position of the power plug in order that I can plug in my iPod speaker. On a return visit to a different room, even without me asking again, they have already reversed the position of the power plug before I check-in. A small matter certainly but shows incredible initiative from the hotel staff.

True the Pen doesn't have buffet breakfast but I find the ala carte breakfast to be very substantial and more refine. Pen's location is better than MO IMHO because it's right at Ginza and the subway entrance is connected to the hotel basement.

Not quite sure why you think Shangri-la is below MO/Ritz and Pen. Hardware wise, the Shangri-la is newer and surpassed all the other three. The furnishing and fittings in the room are of the highest quality I have seen, the bed ultra comfortable and bathroom is a haven for relaxation. F&B is top notch ( esp the Japanese Teppanyaki especially is to die for ) and service excellent too. I stayed at the hotel end of last year and unless standards have dropped recently, I think it's now the best luxury hotel in Tokyo.