Adding a different perspective here — I was a Hyatt Diamond until a year or so before the SPG/Marriott merger, and ended up switching back to SPG because it was getting too hard to make status with Hyatt (my travel patterns changed).
If I could make the stays for Hyatt Globalist, I would absolutely switch back immediately — and I have stayed in at least one of those two hotels. I will probably figure out a way once the pandemic is over and I finally hit LTP.
I have stayed at some incredibly disappointing Marriott properties over the past few years (Courtyard ATL Downtown springs to mind, where they downgraded me to a room without a desk, as a Titanium). I'm not going to lie and say I didn't have similar experiences at a few Hyatt properties. But I have had almost no *exceptional* experiences in several years of stays with Marriott -- and had too many to count with Hyatt. Obviously the industry has changed, but service was a big part of that.
As an aside — while the former AmeriSuites / Summerfield Suites properties deserve extra scrutiny, I've had excellent stays at others. Just pay extra attention when considering them; as
MSPeconomist mentions, the old furniture is distinctive (no arm on the end of the sofa for HP).