While I didn't have the scopes at the same time, I did have the Kahles Gen III K624i and I currently own the Vortex AMG. Both are fantastic scopes with excellent resolution, AMG controls CA much better than Kahles and AMG did better in low light even though the Kahles has a 56mm objective while the AMG is only 50mm. So many have raved about how bright their Kahles was in low light but that was not my experience, and I guess brightness was not so much an issue, the Kahles exhibited almost a cloudy look to it when the light got low while the AMG was much more contrasty. I wonder if something was wrong with my copy and have been tempted to get my hands on another K624i...
You can check out my review here -
http://www.snipershide.com/shooting...t-low-light-tactical-scope-evaluation-part-ii