I've looked through both, although not at the same time/location. The SIII glass is very good. To my memory the glass of the 3.5-21x50mm Bushnell (I assume this is what you mean) was a little bit flat, for lack of a better word. I didn't notice any aberrations or lack of contrast, it just didn't seem as bright and crisp as other $1000+ scopes I've looked through. I also have the 3-12x44mm Bushnell Elite, and comparing it to the Sightron I do not see any "flatness," although the Sightron does have slightly better resolution, comparing them side by side looking at a stop sign and road intersection sign 550 yards away.