For one I think the differences in seasons between N. Tier, and S. Tier plays a big part, 2nd your specific hunting grounds can make alot of difference also. For me I find N. Tier a little easier to pattern during archery. Mainly becasue the deer are still pretty much hitting the latest fall food sources. Find a small apple spot, or nut tree, and wham they move to it very well. I've found in the S. Tier as bucks start feeling their oats things change quickly, and you have to stay on top of things to keep up on patterns. From doe hiding from roaming bucks, to bucks scraping, fighting to full rut. It can keep racking your brains. On top you never know where that buck you saw in August is come Nov.
I can tell you I've seen some different characteristics between the two. For one the S. Tier deer in my area, are big string jumpers. I have to always remember to aim a little lower. N. Tier thats never been a problem. Either way its all good, and I enjoy bowhunting them from late Sept. through Nov.