There's no comparison. As Kagehitokiri says, you could have a legitimate debate between the Four Seasons and the Park Hyatt (which has gotten rave reviews on the Hyatt forum, including by me).

I was just at the Four Seasons two weeks ago, and share ACfly's excellent impression. They were also serving breakfast outside on the terrace, which is a really stunning spot. I think that I slightly prefer the pool area at the Kempinski Cirigan Palace next door, but the Four Seasons is much bigger and newer. And, of course, the rooms at the Four Seasons are nicer (with the possible exception of the top suites at the Kempinski, which I have never enjoyed), although the standard room that I had -- which featured sloping ceilings and a small window -- was a bit underwhelming.

If you're going in the summer and are interested in pool time, then I would choose the Four Seasons. If you're interested in more of a city experience, or if it's winter, then the Park Hyatt might suit your needs better.