I have stayed at PH before in December and spent the majority of my time hanging out at the Cosmo. If you are going to a concert at the Cosmo or just want to try out all the different foods at their restaurants and go to their cool bars I would stay at PH. There is a pedestrian bridge that makes it easy to go to the Cosmo. But PH has the fabulous benefit of being across the street from the Cosmopolitan. If you are going to a concert at MGM or T Mobile or to the pool, MGM Grand is the obvious choice. Otherwise i think it depends on when you go and what you want to do in Vegas. Like others have said, don’t stay in a west wing room at MGM Grand.