I would recommend doing the low light test, set both scopes to 12x and observe details in the bushes and other shadow and high contrast areas after the sun goes down, if possible try and get both scopes side by side so you can look back and forth between both. Years ago I found there was quite a bit of separation with regard to low light performance, but in recent years the manufacturers have really stepped up their game and improved low light performance even in the "cheaper" lines. I'd be curious how the Optika 6 holds up against the Leupold so please share your results.
Yes, the AMG does not have the greatest low end magnification but it does have very impressive FOV numbers (better than some scopes at 5x), similar to your Leupold 3-15, if you look at the FOV compared to the Optika 6 you'll find the Leupold has considerably more FOV especially at the lower end. Scopes with greater FOV allow you to see more at a given magnification which is a benefit.