I find standards between hotels of the same chain to be varying quite a bit. Depending on the hotel and location in question, any luxury chain can be better than the other when it comes to the usual suspects, e.g. Four Seasons, Sheraton, Hyatt etc.

Also much really depends on personal preferences and what is important for you, e.g. elegance vs. homely feel, personal touch vs. arms-length non-intrusive, artsy but smallish rooms vs. larger but less posh etc. etc. etc.

Finding a common ground and definitive answer that can be accepted by most travellers is probably next to impossible IMHO