Andaz is an amazing hotel. We always choose it for the bulk of our time in Tokyo, and usually have our last night at Park Hyatt.
Andaz is the best home base we find. Its location is quiet and clean, the walk to Toronamon or Shimbashi isn't bad at all, Mori tower feels like an Oasis in Tokyo.
The Andaz buffet breakfast is the best i've ever had.
With that said, Park Hyatt has a more comfortable bed and offers 4pm late checkout for us, which works as our flight is always later in the day. Aesop toiletries are amazing and we always try to grab an extra few to stuff my toiletry bag for other trips. Being close to Shinjuku is nice, but at PH we always use their shuttle to get to Shinjuku.