I have the ATS and my buddy has the KOWA. Comparing them, the swaro does beat the KOWA but the KOWA holds in there until last light. Maybe 10 more minutes of light with the ATS.
I would get the KOWA simply because you will be more sure to pack it than the ATS but I pack my ATS everywhere.
The Kowa has slightly more finicky eye placement at the upper power. Optically they are very close. It's our pleasure, as a long standing supporting vendor here, to discuss the different available options and special opportunities with you. Please give a call, 516-217-1000, when you have the time. Thanks
Kowa useful range for me is more like 15-30X. Once you go over that the eye placement gets very picky. Over 40x I consider it largely unusable for practical field reasons. But within its range it compares against the Swaros I've used it against. The weight and size are the main selling points.
I have been looking at the compact Swaro ATC as a replacement just for the nicer wider field eyepiece.
I run both. Both get used. Easier view for ATS but I wouldn't pack it if for a long trip. Kowa gets the job done for less oz. Pick the one that suits your use.
Ill use the ATS for range work, digiscoping work closer to the truck or longer range scoping. If I use the kowa it does all the above with a slightly lower comfort level.