Two very different scopes, both made by LOW but each mfr specs the OEM differently, in the optics world you generally get what you pay for; however, NF has built an extremely strong reputation in the FFP sport optics world while Zeiss is brand new to this game. From an optical design standpoint, the NF ATACR 4-20 is a 5x erector in a 13.9" body while the S3 4-25x50 is a 6.25x erector in a 13.4" body, larger erector (greater magnification range) in a shorter body usually leads to more finicky in the eyebox, DOF and parallax department. Aside from the aforementioned FOV issues, that is something else to consider. I'll let those who've actually had both comment on how the two compare optically but based on the above I have my guess which one likely performs better.
This is really a "in the eye of the beholder" situation. Tunneling in general may not be a big issue for you, what may be a bigger issue is the FOV. If you chose both these scopes because they both start at 4x you might be surprised to see that NF only offers 23.6' @ 100 yards while the Zeiss offers 28.5' @ 100 yards (both at 4x), for me personally that is a significant difference. When I'm looking at scopes I pay more attention to the FOV value than I do the magnification.
MSRP on the Zeiss is $800 less than the NF so this is not too surprising. You rarely see NF ever discounted and they hold their value, but when a company is just starting out and trying to make a name for themselves sometimes they need to price themselves accordingly, so just because a scope is cheaper doesn't necessarily mean it is "cheaper" if you know what I mean.
That is somewhat of a strange comment to make, you don't care much about durability? I'm going to guess what you mean is you aren't too concerned and that other scopes at this price point are durable enough to not make a difference for your use case.
Reticles are highly subjective and we all have our preferences
And yeah, you’d better hope you don’t need the warranty, because it has a time limit, then they start charging you ridiculous “prorated” prices to fix things. 
