I'd like to point out one more aspect of the Gault-Millau debate, namely that the way scores come about plays an important part in the sorts of arguments that can be made against a wine guide.
Gault Millau tastes openly, that is to say every taster knows which wine he is about to score. That has a positive side, as a wine can of course be appreciated more fairly when you have some context to go with it, some experience of the kind of quality that a certain producer has shown in the long range, and other things. The negative side is this: Faced with one producer's range of wines, any taster will tend to give scores that reflect the hierarchy of quality that the pricing suggests, rather than a strictly objective evaluation of every individual wine.
But what's important in the current debate: Open tasting all but invites all kinds of suspicions about bias, preconceived notions, personal score-settling and shady dealings, whether they have a basis in provable fact or not.
The Wein Plus wine guide, on the other hand, makes blind tasting the principle of their business model. Tasters work with anonymous samples prepared for them, so scores are given on the basis of what's in the glass, and - as Metallica would have it - nothing else matters. This has its drawbacks, too, not least the fact that conspiracy theorists will always have doubts, but accusations of unfairness are a lot harder to make.