Those two programs are completely different in nature: SCC does not yield any points (accrued at I-C's with Priority Club), and is paying status-recognition program. Even the base level of SCC, which has no minimum stay requirement, guarantees a good level of recognition.
With neither promotions nor comps, SCC Ambassador is arguably more exclusive than Hyatt Diamond, IMHO (note: I am neither).
As for coverage, I-C is under-represented in North America, but has far better presence than Hyatt in Latin America, Africa, the Middle East, and Europe. Slight advantage for Hyatt in Asia, especially China.
My perception is that I-C and SCC cater to old-school international businesspeople, and Hyatt to a more modern business/leisure clientele.