I'd prefer Hyatt's confirmed suite upgrades over SPG. I have had better experiences with SPG in Asia, but I had just as good experiences with Hyatt and Hilton in Asia as well with only mid level status.

SPG may offer better opportunities but it's simply not clear enough what their policy is. The terms suggest that as Platinum, if a standard suite is available you should be upgraded to the suite, but this just doesn't happen enough (and sometimes the front desk lies or otherwise tries to weasel out of the upgrade). They offered suite night awards where you can be confirmed 5 days before hand, but 5 days is a really short amount of time and your upgrades are tied up until that point. So if you have a planned trip in the latter half of the year, and want to use an upgrade, you have to hope you can use it until 5 days out, only to be potentially disappointed and have wasted upgrade certificates.

I'd rather have half the upgrades to be confirmed at the time of booking and no promise (but just the potential) of a suite upgrade for other stays.