I have to think it isn't going to be the same every year, after all it has been that way since the glaciers. There are spots that one is thicker than the other, I'll need to think about whether there is any pattern to which does better when and where.
I don't have the photos here but I have a couple spots that I hit with 1/2 strength round-up this spring. Some natives popped up, I have one that I need to ID. It looks like switch but is a very dark head and dark seeds.
Another spot that I sprayed had a few Canadian Wild Rye pop up, I'm not sure if there were there before or I had seeds in the cuff of my pants.