How certain is Churchill's later verdict on the R class?

Is there a reliable record of what Churchill thought about the Revenge class during the Second World War?

Only indirectly. Churchill probably disliked the ships, but the surviving remarks come through other people and differ in how severe they make his judgment.

A viewer asks whether Churchill's Second World War opinion of the Revenge class survives in his own words or in the advice he received. Several remarks are attributed to Churchill, but they reach us through other people. The cautious inference is that Churchill regarded the ships badly, while the degree of that dislike depends on which witness is trusted. An attributed remark supports a limited conclusion rather than a precise personal verdict.