I'd guess there's less "piling on". Previously if a comment had a high point score, you would stop to read it, and thus probably vote on it, causing it to have an even higher score. The new system lacks that positive feedback cycle. Top comments still are more likely to get upvotes because of their page position, but there's no easy way to distinguish how much better comment #6 is compared to comment #7 so comment #6 will get glossed over more under the new system.