The argument about the relative skills of keepers like Gilchrist, Kirmani, Knott, Evans, and Tallon can never be fully resolved because there are no satisfactory statistics like Average, Strike Rate, Economy Rate, etc etc to help settle the debate. I'm not saying that statistics are everything, but they are certainly a good guide.
We could look at things like the average number of byes conceded per Test, or dismissals per Test, but ultimately they depend too much on the quality of bowling, the type of bowling, and the pitch conditions. In other words, if **** bowlers consistently bowl the ball 2 metres wide of the stumps then there's not much even the classiest keeper can do to prevent byes, or complete a dismissal.
So all have to go by when assessing someones keeping skills is the personal testimonies of the batsman and bowlers they played with/against, as well as the opinions of expert commentators and writers.
That being said, I've heard few experts rave about the keeping skills of Gilchrist. You get a nod of approval to the question "was he very good", but generally nothing more than that. However, it is not difficult to find articles raving about the sheer brilliance of Kirmani, Knott, Evans, and Tallon. Whether you agree or disagree with all the raving is not the point. The fact that it has been written ad nauseum has to mean something significant.