The real question no one is asking is whether Diamond is ever worth it? For me spending $15,000/year on hotels is a hard ask, especially since most of my travel isn't on OPM. At the same time, I've learned that every hotel chain has serious gaps. Marriott and Hilton have excellent coverage in the Americas but not so great coverage here in Australia. However, Accor has excellent coverage at different price points too here. However, in North America your Accor status is useless unless you are staying in a major city and want to stay at a Fairmont.
Generally no spend-based top tier status is "worth it" if you are looking for value/considering status runs - that applies to both airlines and hotels. It's just a sweetener for those who are going to spend that much anyway (and in many cases are already booking exec rooms or suites so stand to benefit less from the status benefits anyway)
I think at $15,000/year spend you can get Marriott Platinum, Hilton Platinum, IHG Platinum and Accor Platinum for good measure (that works out to 4 chains so $3,750 in spend per year per chain which is doable depending on where you stay at and what promotions you use).
Maintaining all those status levels for $3750/year is virtually impossible unless based in some SE Asia countries and staying at low-end properties where the status benefits are probably quite poor. It would also require spending 192 nights per year in hotels - don't assume these Fast Tracks, double elite nights, and lowered targets are going to stick around next year.
If you
really wanted all four of them, you'd be better off opening an Aspire Amex (US$450) for Hilton Diamond, a Bonvoy Brilliant Amex for Bonvoy Platinum (US$650), Intercontinental Ambassador (US$200) for IHG One Platinum, and go for Accor Plat on spend or cheap Accor Plus nights. In my opinion - and probably the opinion of 99% of AFF - going for all four programs is unnecessary and excessive.
To start, IHG One Platinum from Ambassador is the most useless of the bunch as it doesn't include breakfast, which needs Diamond / 70 stays, or lounge access which need 40 nights for that "reward". Even after the revamp IHG looks the least appealing unless you are very committed to them and go for Diamond.
Marriott Platinum has decent benefits at the moment, although apparently there are rumours of that diluting soon, and there are few properties in Australia making the status less valuable for local stays.
Accor Platinum is obviously a strong option in Australia given their unparalleled coverage both in cities and rural/remote areas, and breakfast/lounge access. Unless you're staying in Ibis Styles or on dirt cheap Accor Plus rates, most Aussies would probably hit Platinum on spend rather than nights by spending >$150 inc tax per night on average.
For me, the sweet spot for status is Hilton Diamond and Accor Plat. Fairly consistent benefits and each of their strengths in coverage complement each other. The redemption sides of the programs aren't the best, but that's less of a priority for me compared with the status benefits.
