Back in grade school, before any of us really had any idea about how baseball or football really worked, many of us could manage to sum up firm opinions about this player or that or one team or another, and make authoritative rankings among them. These opinions were often based on nothing more than a few words overheard from adults, or a memorable name (Drysdale and Coufax were THE sporting names of my earliest childhood), or even just a favorite mascot or color combination. Not yet the stuff of a convincing argument.
There are probably no better BS artists than 5th graders arguing about sports, but sometimes I think professional music critics come awful close and particularly so when they fall into the trap of reducing their criticism to crude comparison ("x's performance of n was better than y's") rather than doing the heavy labor of actually saying something concrete about particular performances. (Here's a recent example, reviewing Loren Maazel guest-conducting the Boston Symph. on a roadshow appearance in New York while Boston's MD James Levine is out of commission.)
Now, comparison can be interesting, particularly when one is able to say something specific about the work in question and articulate how varying performances bring out — or miss, as the case may be — particular qualities or features in the work. And comparison can be practical, useful, as when recommending one recording of a given work from among many available. But when it is reduced to schoolyard BS-ing about a concert which is not to be repeated, what's the point, exactly?
One quality of music — and sometimes I think that it's precisely this quality which recommends music to the angels to practice — is that different performances of the same work can vary to the point of contradicting one another and still achieve superb musical experiences. When we're talking about live performances and not comparing recorded commodities, it's not a zero sum game in which the excellence of one version cancels out others, indeed even when one may strongly prefer one performance over another (i.e. does anyone seriously disagree about Carlos Kleiber's Fifth and Seventh?) the experience of those performances is always going to be made better, more richer, by alternative perspectives.