It seems that opinions are split on whether composition "rules" apply to reflection photo's.
I think it's such a personal and subjective thing, and that people's preferences vary from person to person, and opinions change depending not only on the individual's mood but also on the subject matter!
I like seeing both versions because they can evoke very different responses: Sometimes having reality and reflection in the same shot really works, other times having the mystery of the reflection alone works better!
Here are a couple of shots (one of each type of reflection!) I took in the beautiful Whistler Valley yesterday. What do YOU think?