I was once upgraded at the Bristol to the Prince of Wales Suite and it is indeed a WOW suite. There is also a in suite gym and sauna and the fit and finish of the suite is exquisite.

One of the best aspects of the Imperial is you can walk out the rear of the hotel and be at the Musikverein -- the Concierges at both the Bristol and Imperial can secure tickets to prized concerts, especially for the Vienna Philharmonic.