I wound up getting a Redfield Revolution 3-9x40 over the Vortex Diamondback I intended to buy. After comparing the Revolution, the Diamondback and a Prostaff side by side, I put the other two back and went with the revolution. To my eye, the Revolution sported image quality slightly better than the other two, along with excellent eye relief.
The Prostaff had good clarity, but kind of turned me off with the plasticky adjustment knob covers and overall feel. I imagine it would be tough enough, but when the competition is that close, general workmanship and feel can be a deciding factor. The specific Diamondback I was looking at had a whiteish-silvery tinge that crept into the field of view at times... I think it may have been light from the store's skylight, but neither of the other scopes had this problem. I wanted to look through another non-display Diamondback, but, as it turned out, the display model was the last one in the store.
firme67, have you made your scope choice yet?