This is a tough question because I have changed methodology depending not just on the quality of the beers but on many other factors.
In general, I sip a little of each beer to see first but if beer A is light and really good and the rest of the tasters are darker, I may polish off the light one to not wreck my palate. I also sometimes try to find what exactly a flawed beer has wrong with it and thus finish it, before I go back to the best beer of the bunch.
If all the beers are of equal quality, and one is not a stylistic outsider, then all will be drunk at the same pace. But if all beers selected are not good, and it has happened. I may drink the best one and drink enough of the others to obscure my dislike when I bring the glasses back.
It is not an easy question to answer because of the Choose Your Own Adventure decision tree involved.