I don't think it is all the placebo effect. If you can't feel the difference between racing sew ups and marathon pluses you just aren't paying attention. The difference between very stiff and very supple sidewalls is pretty pronounced. If we are talking subtle differences between similar tires you have a point. I don't know if the difference between Gatorskins and Compass models is enough to be noticeable or not, but I am curious enough to want to know. It may wind up being a waste of money if they either are too prone to flats or don't ride much different.