Although it is convenient to generalize I always go for the individual hotel rather than what chain it is part of. For instance the George V, Four Seasons Florence and Istanbul are far different properties from the Four Seasons Vancouver. Similarly, I do not always think Shangri La is a top luxury chain but the one in Paris certainly is imo. I guess what I'm saying is do not rely on a chain's reputation, check out the specific property at which you want to stay.