Much of it is for show. These guys are prep'd and propped up, and fed answers, told how to gesticulate, what facial expressions to make, etc. Some more than others. It's all part of the great dog and pony show. Enjoy. :-)
My impression of Barry is that although he is subject to all these forces, he actually has a core of capability in natural self-expression, articulation, etc. Perry... not so much. It's up for the voter to decide if, and to what extent that matters.