I've been cross posting my Blogger posts to Google+ for the past few weeks and I've noticed some differences in the comments between the two. Blogger tends to get fewer (often much fewer) comments, but the comments themselves are frequently longer.
Google+ tends toward more but shorter comments. It's more immediate and less polished in general, but definitely more lively.
This post: What Are Your 5E Deal Makers / Breakers? had 9 comments on Blogger, 266 on G+. Admittedly, the G+ thread had some cross talk going on, but that's still a factor of 1 to 26 in terms of comments.
I'm interested in the next integration step between G+ and Blogger, as I suspect it will blur the lines between the two.