Greetings and thank you for your interest in Primary Arms Optics. A product comparison with values of 500.00 verses 1,000.00 will go toward the product valued at 1,000.00.
When it comes to glass there is some personal preference involved, I have not personally handled an Athlon Ares so I can't speak to the glass.
With the Primary Arms 3-18 50mm the glass is on par with other optics in the industry in the same price range. Vortex has great glass and in regards to the Crossfire II, the glass is comparable.
In regards to tracking the scope is very durable and can hold zero pretty well. It's tested on a SAR 17 308 which kills most optics.
I hope this information was useful, good luck with your purchase and if you need additional details about glass, and it's not protected info, we can get you an answer.
Happy shooting!