What is the difference between a trial judge and an appellate court?

It cannot be disputed that a trial judge, in dealing with witnesses, enjoys an advantage over an appellate court in assessing the value and reliability of witnesses (Joyce v. Yeomans [1981] 2 All E.R. 21 at 26). And this advantage, in the present case, is in my view, the overriding consideration. Although, as I have said, it is clear that the experts did not say what the trial judge understood them to say, it is by no means clear whether their testimony discloses a sufficiently firm practice in the industry to justify one conclusion over another. Further, the questions put to the experts were such as, in my view, to make it virtually impossible for an appellate court to conclude which circumstance or circumstances of those put forward in the hypothetical questions were the determining factor or factors in establishing entitlement under industry practice.