The Kahles 3x18i would be my pick. I prefer the Kahles glass over the Votex. The other reason i like the 3x18i is it has a 34mm tube which just looks better to my eye then a 30mm tube.
I've had both, both are great scopes, both can get the job done. The AMG has plenty of FOV at 6x so if it was purely a PRS rig I might be tempted to go for the AMG. Both have great turrets, AMG is 10 mil while Kahles is 16 mil, both have great clicks but the AMG has locking turrets while the Kahles has a seemingly useless feature called twist guard. The AMG is cheaper and has a better warranty. Glass wise that is tough, while I do not have the scopes side by side both would be tops, AMG controls CA slightly better. Reticle is personal preference, I like both. Obviously the K318i is much shorter but the AMG weighs less, unless you are putting this on a DTA Covert I doubt the AMG is going to be an issue, the K318i "looks" better on AR style rifles but again - personal preference.
Here's a couple pics, Kahles K318i on top and Vortex AMG on bottom
Kahles without a doubt. IMHO the only thing Vortex has on the Kahles is price. You will 100% get what you pay for with an manufacturer like Kahles. Vortex is fine for most things, however on something like a comp rifle I would want more than fine.
Both would work fine and both are very nice scopes. The choice would ultimately depend on your style of shooting and whether a bit more magnification is important for you.
Also, Kahles' center parallax turret is better for left handed shooters.
For me personally, if price was the same, I'd likely go for K318i since the magnification range fits the way I shoot a little better. However, I suspect you can get the AMG for a bit less than K318i, so for the money it is a better choice.
In other words, I am in no rush to sell my AMG to get a Kahles, although to be fair, I also have TT315M which I prefer to K318i.
In terms of reticles, I think I like SKMR3 a little more than EBR-7, but I do not think there is quite enough difference there to matter.
Koshkin, I appreciate your advice, as I look to your advice as an expert in optics, thank you. I like the SKMR 3 better, so I think I’ll stick with Kahles.