I think Terry's theory on one type on the top and different on the bottom is valid. I've been using it for years and 90% of what I'm doing is in trees.
Here's another tip I use for those that hunt from hardwood trees. One of my favorite stand locations has a multiple trunk situation that I prefer, but they are small and the tree is on a knoll that the deer like to cut across above or below. Since it's a maple tree, it drops it's leaves in mid to late October and then I'm more likely to be seen from certain angles. At the beginning of each hunting season, I trim some limbs from pine trees and tie them off to the maple limbs extending off around my stand. Not too many, but just enough to break things up a little (the little bungie cords work well for this). Since their up before leaf drop, which is usually gradual, the deer seem to be used to this "funny looking pine/maple" during the rut and late season. This is on my parents private land, so no issue with the cutting. There are some commercial products out there that would accomplish the same thing, but I think it's important to get them up before leaf drop so that it's not something "new". This is the only tree that I do this with, because it's the only place that I really want to be, but no other options.
I think this is a great topic and as Terry says, it's "opinion" but I think valid from my point of view.