There are varying perspectives with regard to what is in "the readers' best interests". I believe that what is in the readers' best interest, both in printed guides and here on the DIS, is helping prospective guests understand what they can reliably expect: Not over-promising, because guests have a chance of having some specific, great experience, nor under-selling, in an attempt to have a criticism carry more weight.
Personally, and more specifically, I believe that the Official guide's biggest problem is that it limits itself to outlining only the "reliable good" -- it doesn't outline any of the "reliable bad", and underplays how "unreliable" a lot of the "good" and "bad" is. By contrast, the Unofficial guide's biggest problem is that it doesn't adequately emphasize the "reliable good". I find it also over-emphasizes both the "reliable bad" and the "unreliable bad". I also worry about how, in some cases, it showcases the "unreliable good".
As I mentioned above, IMHO both books are inadequate on their own.