Well, hmmm. Guys I'm going to have to back off my claim of 'much softer'. In shooting pictures that were the same at both 70mm and 200mm for examples I'm not finding a lot of difference. The 200mm end is a little softer, but not that much.
My original claim came from what I saw in pictures using this lens to shoot sports, motorsports, and the such. I don't shoot charts or 'test' pics much, just real use stuff. I guess I'm going to have to go back to those and look at the exif to try and figure out what is going on.
I do appreciate the responses, and especially the suggestion to shoot pics so that the scene is exactly the same at both focal lengths.