Funny you should ask that question as I was in the exact same position late last year while planning my trip scheduled for the end of September (which is now seeming less and less likely to happen). At the time, FS Otemachi was not open for reservations so I booked Shangri-La as a placeholder given the rate was reasonable and reviews appear to be universally positive. I liked the prospect of having access to the Horizon Club (complimentary access for all suites) to provide additional space to relax as my family adjusts to the time change during the firsts couple of days. That said, we are very loyal Four Seasons customers and excited to have an alternative to Marunouchi which is lacking in terms of amenities and seems a bit dated. When Otemachi opened its books, I was shocked to see how competitive their rates were. I realize this is due to the fact that they will still be in the process of ironing out the kinks, but took comfort that they would learn a lot following the Olympics crush. Given the current state of affairs, their ability to offer a polished product may now prove to be a bit more of a challenge, but I'd be willing to roll the dice a bit to enjoy the fresh hard product which I'm sure will be stunning. As of right now I'm playing the "wait and see" game should the world return to some semblance of normalcy and I'm actually able to travel and will monitor reviews post opening and make a decision closer in time. If were in your shoes, I'd book FS Otemachi to lock in the fantastic rates as well as a second choice just in case you need to jump ship. Happy planning!