So ended up staying at all three during my time in Seoul.

I would say Aventine hit it right on the head with their takes on which properties are the best and worst in the various categories. My only disagreement is I would hand the worst Globalist treatment to Andaz instead of GH. Admittedly part of my take on this may be folded into the not-so-great level of service that I received at the Andaz during my stay. I found my treatment as a Globalist at the GH to be fair.

I would definitely stay at the PH and the GH again. The Park Hyatt Seoul was the first Park Hyatt I stayed at, and it was a really great experience. I would love to stay there again.
The Andaz Gangnam was the first Andaz I stayed at, and I don't think I'd stay there again unless I had something going on in the immediate neighborhood vicinity that I needed to attend, or the price dropped by a decent amount.