In 2020 I have used Hyatt Privé, IHG Luxury and Lifestyle, Shangri-La Luxury Circle, Marriott Stars, FHR and bookings through Centurion. My take:

- In terms of guest experience I give an ever so slight edge to Amex. For example Park Hyatt Hamburg gave me lounge access on an FHR booking but not on a Hyatt Privé stay. (I used FHR online, no Centurion agent involved). I have no insight as to why that is but my guess is they want to keep Amex (and their clients) happy.
- In general I find all the programs very similar and I am happy with all of them. FHR gives a 4 pm late check out though. Not all hotel programs guarantee that.
- There is not much daylight between FHR and an FHR booking through Centurion. Of course the difference is there for Centurion FHR hotels such as Waldorf, St Regis, Mandarin Oriental and a few other brands. Those are very generous for Centurion card holders (multiple upgrades often and 300 USD credit)
- I found, very odd, that all hotels know FHR but they do not always know their own hotel program. At one time I had to explain at check out what the Stars program is to get the benefits. Also at an IHG property they really had to look closely at the Luxury and Lifestyle T&C's at check out.
- FHR has the advantage (in my country) of online booking. No such thing for the hotel programs or Centurion. My NYC travel agent and my Centurion RM are quite responsive though (I am located in Europe). FHR disadvantage is the limited list of hotels so the other programs fill the gaps.
- Upgrades: obviously sometimes you get lucky, sometimes not but there is 95% probability of an upgrade. Not much difference between FHR and hotel programs. I did have a few spectacular FHR upgrades in the past but I am not sure the numbers are statistically relevant. My Stars sample size is small but upgrades were not the best. I noticed Hyatt and Shangri-La confirmed upgrades a few days after booking. Anyhow, upgrades are normally not my main concern. I appreciate early check-in and late check out if/when needed much more.