I concur that the PH Istanbul is one of the best PH stays we've ever enjoyed. I don't think you can go wrong by staying there, and our stay was in Oct 2014. We were very impressed and really loved our stay. Food/beverage and service were to a very high standard here. Our Executive Park Terrace Suite was fantastic.

I absolutely agree that the Park/Spa suites at the PH are less desirable...and not even real suites. They are darker than I'd prefer. If comparing those with other hotels, I'd look elsewhere.

We despised the Kempinski Ciragan--as the beautiful palace building had mostly suites that were ridiculously overpriced, and the main building was ugly beyond measure.

We weren't overly impressed with the FS Bosphorus, actually. We found the Bosphorus view rooms and suites obscenely overpriced for what you go, and we weren't fans of the more formal ambience and marble showcase. The FS Sultanahmet was a much more intimate and beautiful property in our view, but we didn't love the location beyond its convenience for touring the major sites (which we did in a day!). The FS Sultanahmet was also very expensive and not totally worth it in our view. But between the two, we'd take the FS Sultanahmet.

If we were to return, we'd almost certainly choose the St Regis. But it sounds like the StR, PH, and Raffles are all worthy contenders.