Besides their quality construction and durability, the Nikor kit have something else going for them.
Compared especially to plastic alternatives, the Nikor reel winds have a relatively small contact surface with the film and good spacing. This encourages good fluid exchange across the surface of the film as you agitate. For the ordinary case, this results in consistent development at the edges of film.
Where it really shows up is if you do semistand or EMA extended, low agitation development. The high walls of other reels - again, especially plastic - will cause developer trapping along the edges and will cause all manner of bromide drag nasties. Even with the Nikors, you have to suspend the reel well above the bottom of the tank (I us and inverted funnel) so that gravity can do its job and drag the development byproducts away from the film. But the minimal contact an wider wind spacing makes that gravity draining work pretty well.
I also like the Nikors for their ease of maintenance and cleaning. A quick rinse and you're done. With black plastic, I'm never quite sure the ghosts of the last developer or fix have been entirely expunged
This is not to say there are not other quality stainless systems available, but I haven't personally used them. I will say that the one time I strayed from Nikon and got a different stainless tank & reel system, it came with a plastic lid that snapped into place. Imagine my horror when I discovered that at least one of those lids had not been properly manufactured and was so thin it was leaking light upon my film. I promptly ceased any use of those lids (though the tanks were entirely usable).