I had a 5.5-22x NXS in the recent past. Excellent scope....rugged internals that are very repeatable and decent glass. I've not experienced the other two scopes you have listed....mainly because I'm interested in having more internal adjustment range that a 30mm or 34mm main tube offers versus a 1".
You didn't say if weight is a really big issue for you. If so.....the Swaro is the obvious winner at 17.5 ozs. If you can stand an additional 9 ozs of weight over the Swaro.....the Zeiss gives you more internal adjustment.....for your longer shots. The NXS is heavy because it's built to withstand punishment and continue to work flawlessly. If you need to have something that will hold up....NF won't let you down.
I think you'd see a slight difference with the glass if you did a side by side comparison. The HD glass in the Swaro and Zeiss would have the edge in clarity, color rendition and so on. The NXS does not come with HD glass.... you would need to step up to the NightForce ATACR 5-25X to have HD glass and thus a direct comparison with the Swaro and Zeiss. The NXS has nice glass.....but isn't quite like an HD version. Might be a consideration if you plan on spending a fair amount of time behind the scope. I find I have less eye fatigue when I'm behind my Premier or Kahles versus an NXS or my Sightron S III's.
One last thing....I can attest to a warranty / customer service experience with NightForce. I would rank them right near the top of any manufacturer here. I've had experiences with Premier Heritage, NF, Leupold, Bushnell and Burris. I would rank them highest to lowest in the order I listed them. Not sure what Swaro and Zeiss have.....but if the scope had to be sent to Europe for any warranty work...that might also be a consideration.
Good Luck,
Wayne
