I have the Vortex Diamondback 4-12x40. It's seen use on ARs, .308 bolt guns, and a .243 bolt gun. Dropped, fallen on, and banged around and it never lost zero once. I'm looking to mount it on my Mini-14 now. I have a Redfield Battlezone 3-9x42 that is back on my .308. I've been looking to change it but it works so well I'm thinking I won't. You do get some weird gold tinge rarely in very bright sunlight but you never lose the reticle.
The glass is clearer on it than my Vortex, even though I gave up some magnification the RF is just better. It also has 2 dials for shooting out to 500 with .223 and .308 if spinning dials are your thing. Plus you can actually use it to range a target with the tac-moa reticle. Warranty is a dead heat, Leupold (owner of RF) and Vortex have stellar customer service. I hear the Redfield Revolution scopes are even better than the other RF lines. Just like the Viper and Razor line from Vortex are better. The prices are on the lower end for both and I wouldn't shy anyone away from either company.
I'm a budget hound. If I find something that works well for me I tell others about it. Everyone loves a bargain and with RF and Vortex you get more than what you paid for. Also don't just look at Vortex, Leupold has some very affordable scopes that are just excellent like the Leupold 6-18x40 Mark AR MOD 1 Riflescope that can be had for $550 at swfa.com. My buddy has one and just loves it. If you are not using a rangefinder then I would suggest a moa or mildot reticle.
Now that I'm thinking of it I just ordered the Primary Arms 1-6x24 ACSS reticle with a 30mm tube. It looks to be shaping up as a very nice bang for the buck lower powered optic. I might do a review when I get it in. Good luck with your scope hunt!