As an introvert, I would say there is a difference. Deep here is in the eye of the beholder and I agree with idea that a deep conservation doesn't drain me and can in fact be energizing. Comfortable conversations are more on the fun and light sight but they can be an drain on my limited social energy reserves. I like them, but I need recovery time. The 'deep' part may mean different things to different people but to me its one where knowledgeable people are discussing aspects of that knowledge at a, well, deeper level than most conservations allow for.