Why it's a strong contender for "best":
* Price: This is a HUGE factor. Compared to the Nikon 600mm f/4 TC VR S or even the 400mm f/2.8 TC VR S, the 600mm f/6.3 VR S is significantly more affordable. This puts super-telephoto reach within reach of more photographers.
* Portability: It's remarkably lightweight and compact for a 600mm lens. This makes it far more manageable for handheld shooting and traveling.
* Image Quality: The "S" designation indicates Nikon's highest optical standards for Z mount. It delivers excellent sharpness, contrast, and resolution, especially in the center. Edge-to-edge sharpness is very good, and chromatic aberration is well-controlled.
* Vibration Reduction (VR): Nikon's VR system is highly effective, helping to stabilize images and videos, especially in challenging lighting conditions. This is crucial for such a long focal length.
* Autofocus Performance: It features a fast and accurate autofocus system, keeping up with action and wildlife subjects.
* Compatibility with Z Mount Teleconverters: Can be used with the Z TC-1.4x and Z TC-2.0x teleconverters to extend the reach even further (to 840mm and 1200mm, respectively), though you'll lose some light and potentially some autofocus performance.
Why it might *not* be the "best" for *everyone*:
* Maximum Aperture (f/6.3): While not a dealbreaker, f/6.3 is slower than the more expensive options like the 600mm f/4 TC VR S. This means less light gathering ability, potentially higher ISOs in low light, and a shallower depth of field (although at 600mm, depth of field is already shallow). The slower aperture also means the viewfinder image will be dimmer.
* Optical Perfection (at a cost): While it's very good, the 600mm f/4 TC VR S will inherently have better sharpness and better bokeh/subject isolation due to its wider aperture. But you pay a LOT more for that improvement.
* Specific Needs: If you're shooting in consistently very low light or need the absolute maximum image quality, the more expensive, faster aperture lenses might be a better choice. If you absolutely require the highest possible frame rate in burst shooting situations, the flagship telephotos might perform slightly better, although the 600mm f/6.3 is still very good.
Alternatives to Consider (and why they might be better or worse):
* Nikon 600mm f/4 TC VR S: Superior image quality and wider aperture, but significantly more expensive, heavier, and bulkier. Has a built-in 1.4x teleconverter.
* Nikon 400mm f/2.8 TC VR S: Extremely fast aperture, excellent image quality, and built-in 1.4x teleconverter. Very expensive.
* Nikon 180-600mm f/5.6-6.3 VR: A good alternative if you want more zoom flexibility, and it's also less expensive. However, it's not quite as sharp as the 600mm f/6.3 VR S, and its autofocus is likely not quite as quick.
* Using F-mount telephotos with the FTZ adapter: While this works, you're adding an adapter and the performance might not be quite as good as a native Z-mount lens.
Conclusion:
The Nikon 600mm f/6.3 VR S is a fantastic super-telephoto lens for the Z mount system. It balances excellent image quality, portability, and affordability in a way that makes it a compelling option for many photographers. It's arguably the "best" choice for a lot of people because of its price/performance ratio. However, if money is no object, and you need the absolute best image quality and light gathering, the 600mm f/4 or 400mm f/2.8 might be worth the investment.
Ultimately, the best lens for *you* depends on your specific needs, budget, and shooting style. Consider what you value most in a super-telephoto lens, and then weigh the pros and cons of each option. I would strongly recommend reading and watching reviews and ideally trying the lenses out if possible.