Nothing much to add to above. The Regent is not yet branded to the newest standards and would generally need a little hardware update. Staff is outstanding.
The two hotels are very different. If you're looking for a very classic, personal, "small" place it's the Regent, if for a vibrant place, then IC.
Originally Posted by
DonPedro
IAN MORGAN gives a great summary.
Only thing I’d add is that in a city as spread out as Berlin, take location into account too. IC Berlin is about a 12-15 minute walk to the nearest (Zoo) station to get anywhere.
Regent, you’re in the heart of Mitte and can walk to all central sights and museums.
Bus 200, which is - together with 100 - one of the unofficial sightseeing buses of Berlin, takes you to the major sights and stops right outside the hotel.