Following up on my post from several months ago where I was trying to decide between the PH and the GH, I wound up staying my first night at the Grand and my second night at the Park.
Overall I think I actually preferred the Grand. I found I actually got better service at the GH than the PH myself. I didn't have any tricky requests, I never really did anything except check in and out, but all the Park Hyatt staff I talked to seemed kinda disengaged, as if they were waiting for somebody more important than me to show up.
Other comments:
1) Grand Hyatt had a large, well-furnished room. Park Hyatt had a much larger, slightly better furnished room. I can see how people staying a week or more would prefer the extra space of the PH, but to me it was just surplus to requirements.
2) GH was kind enough to give me a south-facing room on the fourth-to-top floor, with views of the river, Federation Square, the Botanical Gardens, Government House, Eureka Tower, Port Philip Bay, the Dandenongs... well, everything really. Very impressive.
3) As a lowly platinum, the GH promised me at checkin a "food and beverage amenity" which never actually arrived. (Actually I went out for a few hours and left the "do not disturb" sign on, so it might have been my fault.) PH didn't promise me anything at all. So let's call it a tie.
4) Location is a clear win for the GH (unless of course you need to be at Parliament or something). Sure, it's only a few blocks further, but the GH location is hard to beat for convenience.
5) On the issue of room noise: it's true, the doors are oddly thin at the Grand Hyatt and you do get noise from the corridor into the room. I don't know why they didn't fix this in the big renovation. But the number of actual seconds of my stay that this actually bothered me was maybe fifteen, because there wasn't actually all that much traffic in the corridor. Oh, and the gap is nothing like one inch.
6) One more nitpick on the Grand Hyatt: the clear glass shower cubicle is located just a few inches too close to the toilet, and every time I bent down to sit on the toilet I'd bang my head on the glass. A few stickers on the glass would solve this problem. Or maybe I'm just an idiot.
In conclusion, if I were to do it again (which I won't, because in a couple of months I'll live in Melbourne) I'd probably go with the Grand Hyatt. Unless I were staying for an extended period of time in which case I'd go Park Hyatt just to get the bigger room.