You haven't finished figuring out the costs, I think.

What is included in each room?

While the Priority Club Select card gives you automatic Platinum status, that gives you no chainwide benefits. You have to research whether it gives you any benefits (like free breakfast and/or free internet) at that particular hotel.

I'm not that familiar with Hyatt, so I'm not sure what elite status level you get with the card and what that means in terms in-hotel benefits. Others will have to chime in on that (or you'll have to figure that out yourself).

I'm not sure about Singapore, specifically, but in all too many countries breafkast and internet can be high-cost add-ons if they're not free (either due to the hotel, due to the room rate, or due to your status). But of course, it also depends whether you care about those benefits at all (not everyone does).

Finally, are there any significant differences with location? Again, I know nothing about Singapore, but in some countries one hotel program has a less fancy hotel in a great location while another hotel program has a fancier hotel but in a more isolated, less practical location.