I've had several Redfield Revolutions and several Vortex Vipers, no Diamond backs or Crossfires.
Pricewise, the Viper runs double what a Revolution does.
Last fall, before deer season, I took a 3-9 Revolution, 3-9 Bushnell Elite 3200 and a Burris Fullfield 3-9 down to edge of the field. I sat there for the last hour of daylight and compared the three.
My conclusion was that all three were very comparable. I gave a slight edge to the Burris in light gathering, clarity. The Redfield and Bushnell I could not tell a difference in.
I think either of these three scopes are very adequate for woods "whitetail hunting". I've had all three of them out in rain, fog and snow and have had no issues. If all of my shots are less than 100 yds, I wouldn't consider dishing out more than $150. All three of these can be picked up for less than that in like new or slightly used condition.
I also did the same thing with my 4-16 Viper, 4-16 Steiner and 4.5-14 Burris Fullfield.
Again, I thought the Vortex ran neck and neck to the Steiner with both of them having a slight edge to the fullfield. Of course, the STeiner is double the money of a Fullfield and $200 more than the Vortex.
My biggest issue with the Vortex is that in bright sunlight, it tends to glare. Vortex is the only scope I've ever felt like I need to have a hood in full sun.
Just another opinion.