Well, that would be an interesting question. Clearly the deeper posts tend to acquire fewer votes, but is it all because of depth, or it is (also) because the perceived quality of the posts is greater the "shallower" they are?

Follow-up posts tend in general to be progressively less pithy, more OT, and in some cases, less courteous.

But remember that you only need one upvote to gain the first XP on a post, so prolific output of varied quality may have an advantage over less frequent, higher quality posts. Certainly it seems to me that the overall "winners" are those who strike that balance the most.