With Dubai being so spread out, if you don't have points status anywhere, then better to choose location close to where you think you'll be spending a lot of your time, to avoid really long taxi rides up and down Sheikh Zayed Rd. Park Hyatt is on the Deira side of Dubai Creek - close to the airport and 'old city' (such as it is) whereas Grosvenor House is about 36km away near Dubai Marina.