I don't have detailed pics for full reviews, but just returned from stays at two IST Marriott properties with some info for anyone interested. For reference, I'm Bonvoy gold status, not a blogger, nobody special, just a casual traveler who tries to make an international trip with my wife at least once a year.

Orientbank Autograph Collection-
Booking- As a follow-up to my earlier post, I kept my reservation at Orientbank despite not finding a single review anywhere online. After sending some e-mails to the hotel, they assured me they would be open for my arrival. I booked using three 35k free night certificates I had stashed. While this is a category 4 property and I could have made "better" redemptions at the cat 5 RC and JW marriott, the property intrigued me and we liked the location (the cash rates were also well over 200 EUR/night when I booked).
Arrival: We arrived around 23:00 after a very long travel day and multiple staff hurried outside to help us with our gear from the taxi. I thought this was kind of weird for that time of night, but not unheard of I suppose. When we entered the hotel, we were shocked to see a large staff waiting for us. It turns out we were allegedly the first guests of the hotel, explaining the lack of any online reviews. They greeted us with a champagne toast with the general manager and introduced us to the staff. You could tell they were very proud to finally be opening the hotel as it had been in upwards of a 10 year project, which was likely further delayed by COVID.
Status recognition: They didn't specifically mention my gold status, but thanked me for being a Bonvoy member and upgraded us to a Deluxe king room, (I think the award reservation was for a standard king). The check in agent also stated we would get a 2000 point bonus (I'm not really sure what for, but it did hit my account already and was separate from the standard 500 point gold member bonus which also posted). We were also given late check out, which was initially for 4 pm, but they ended up letting us extend that to 6 pm.
Property: The property is really pretty stunning. It is in the renovated Deutsch Orientbank building (James Bond fans will recognize this as the building Daniel Craig exits at the beginning of Skyfall). I wish I had pictures to share, but the photos on the website and hotel's social media are fair representations. It's a fairly small hotel, I counted less than 40 rooms. One thing to note, the website has some pictures of the rooftop suggesting there may be rooftop access. I attempted to access the rooftop and there was a locked door with a staff only sign. I'm not sure if there's plans for anything up there in the future, but not able to go there at this point.
Room: We arrived to the room to find a plate of a variety of delicious turkish delight. The staff had also prepared us a few boxed meals with sandwiches and fruit as they knew we had been traveling, which was much appreciated. As noted above, we were upgraded to a deluxe king room. Our room was beautiful and had limited views of the Bosphorus and several nearby mosques. I will say this room was not very large by American standards, but on par with most European rooms I've stayed in. Later in our stay I peeked in a room being cleaned that I assume was a standard king and it appeared to be quite smaller. Also, the toilet is in close quarters with everything, so probably best to stay at this hotel with someone you are very close with. Amenities were great with extras such as exfoliating body scrub and loofa, bars of olive oil soap, toothbrush/toothpaste, etc.
Food: The website claimed breakfast is included for everybody, which is another reason we decided to book here over RC and JW Marriott. This was the case for our stay and they pretty much let us treat the full breakfast menu as a-la-carte and we were not upcharged for anything. The food was amazing and really was a highlight of the stay. The Turkish breakfast was delicious and they just kept bringing out food to the point I was embarrassed that I couldn't keep up eating it all. The poached egg with smoked salmon and healthy breakfast bowl (basically a salad with smoked salmon) were very good as well.
Service: This is an area where the hotel really shined. As alluded to above, you could really tell the staff was proud to finally have the property be open. Everybody was extremely professional and eager to help us with any requests or information about the local area.
Location: The location of the hotel is really great if you want to be near Istanbul's old town (Sultanahmet). It was a short walk to the Aya Sofia, Blue Mosque, Grand Bazaar, etc. If you want to be centered around Taksim, there are better options.
Conclusion: We loved this property and am so glad we kept our reservation. The staff was truly amazing and made us feel so welcome. The breakfast was really delicious and that alone made this a great use of some 35k free night certificates in my opinion. I really hope this property succeeds, and I wouldn't be surprised to see it jump up a few categories in the next few years.

Sheraton City Center: This hotel has been reviewed multiple times on FT, so I'll be much more brief here. After leaving Orientbank we moved to Sheraton city center which had a good cash rate (around 100 eur/night with breakfast included when we booked). While status was never formally recognized at check-in, we did automatically receive a late check out to 4 pm. They also happily extended this to around 6 pm while we used the spa on our last day. No room upgrade was offered, though I never really expect this with Marriott gold. The room was spacious and in great shape, you could really tell the hotel was only a handful of years old. The breakfast was good enough, but flavor-wise not even close to what was served at Orientbank. There were extensive options with staff behind plexiglass plating up buffet style dishes you pointed at due to COVID. The location of the hotel was the weakest point with probably a 15-20 minute walk to Taksim square, which wasn't a problem for my wife and I as we typically prefer to walk. That being said, the hotel does have a free shuttle to Taksim that leaves and returns every hour throughout the day. We used this a few times and it ran very smoothly.
Conclusion: We also had a good stay here as many others have reported on FT. I thought it was a great value for the cash rate and if you enjoy walking or would utilize the shuttle to Taksim it circumvents the less than ideal location. Would definitely consider staying here again if looking to save some money, but there are other Marriott options in better locations in this general vicinity such as JW Marriott if money isn't an issue.