I have found Embassy Suites to be a has-been chain of yesteryear. Mostly dumpy and/or tired properties.
As far as Hilton/Marriott, you can tell both points programs to default to your favorite frequent flier account, so its all the same in the end.
Marriotts are more liberal with a cancel before 6P policy, Hiltons are different from one property to the next, typically 3 PM.
The ones I have stayed at; Hiltons are newer, Marriotts older.
I tend to avoid Residence Inns because they tend to be a white-trash crowd, not that anything is wrong with that, but, just saying....
But I agree, you are splitting nano-hairs
** there are some newer Holiday Inn Express hotels (McAllen for one) that are actually pretty nice and good for that last minute trip or weather diversion.