I used to stay at the Grand Hyatt Berlin many many times for the last 10 years, but their management (not the regular staff) has driven me away. Now being an RA, I have started staying at the IC. I prefer the lounge offerings at the IC. Upgrades are also better (am Hyatt Diamond as well, but while they used to go an extra mile years ago, since the GM changed, it's a 7th floor room at the Hyatt and lounge access and that's it - no suites). The IC also seems to be consistently cheaper than the Hyatt, and I see nothing that justifies the price difference in favor of the Hyatt.