If you look at the specs for the K525i compared to the ATACAR 5-25X56 F1, you will see that the Kahles is somewhat lighter and shorter than the ATACAR and that its minimum focus distance is 20 meters compared to 45 yards for the ATACAR.
The ATACAR has substantially more elevation range than the Kahles, which is surprising as they both have 34mm tubes. The glass in the ATACAR is HD, but I cannot find any information on the glass of the Kahles at their website.
I know of several shooters on the line who have Kahles, the K1050i model, and they like them, but the glass is underwhelming.