In my not-always-humble opinion, I think that a huge amount of these differences (and people's opinions of them or the overall nature of one board vs. another) are quite often (though not always) splitting hairs about something that's already an exceptionally fine instrument.
ANY of these Nords will be fun to play, will bring a smile to your face, and will sound fantastic. Will they each sound exactly the same? Can you do exactly the same thing with each of them? No, but that's not the point. Almost any Nord will get you 'close enough" to the sound you want for a cover band, a live gig, or what-have you. They'll also get you into gorgeous new sonic territory perfect for whatever you want to cook up on your own in the studio. But they aren't clones and I don't think they're intended to be clones of anything - even the Rhodes models and piano choices show that Nord is specifically looking for characterful base instruments on which to build a vibrant, enjoyable platform to build your own sound from, not to duplicate in precise nature an existing sound.
As a corollary, any of these Nords will also make you bang your head against at wall at some point saying 'it doesn't do THAT? NOOOOO' but if you take a step back and think about it, very little on the planet is likely to actually DO that (maybe one other keyboard or instrument, sometimes not even the real thing, like transitions, for instance) at all. So in reality, while they aren't read-your-mind dream machines, they do so much already to get you to a gorgeous sound (sometimes with a little creative thinking and the realization that maybe working within reasonable limits is a valid creative process after all) and you will end up an extremely happy person.
With that said, my personal experience playing quite a lot of diverse brands of keyboards and being able to be content no matter what keyboard I find myself playing (but still having strong preferences for what I'd ideally like to have), the NS3C waterfall keyboard is, IMO, a perfect compromise between piano, synth, and organ. Now, I'm not a hammond purist, I come from (simultaneously, as it were) the classical piano world AND the synth world, I can use a Nord Lead as a PianoTeq controller and be "ok" with it (although I'm not likely to play or even want to play a Mozart concerto on it!), and I certainly don't care about needing to cover somebody's exact moves on an exact vintage keyboard at some point in their concert career. So, take this all with your own preferred version of sodium chloride. But... in MY experience, the NS3C keyboard ROCKS. It's very similar to the 61-key keyboard in my Prophet Rev2 which is nearly identical to that in an Access Virus KC I played and loved, which is many synth-head's ideal keyboard, but at the same time, the slight differences give it a little different weight and feel that somehow work very nicely for piano control of dynamics, return and retrigger, etc., without even being a hammer-action board at all. So to me, it's really a near-perfect compromise and if you changed anything in any direction, I'd bet as many people would be off-put as would be pleased, so that's winning, if you ask me. The Electro 5 and 6 both have very agreeable waterfall keyboards, and my old Stage 2's HP76 had a very playable action as well, although I'm far more likely to try to emulate keith emerson on the compact than I would be on the HP, just because one time I tried a couple crazy hammond-style glisses on a Kurzweil and tore a fingernail pretty badly mid-concert.
So sure, go play a few of them, trust your fingers, but in the end, if you're deeply in love with the features of one of the keybeds you didn't prefer head-to-head as much, trust me, you'll adapt super quickly and end up loving pretty much any of them. Unless you're insanely picky and absolutely cannot be human and adapt to a changing environment, in which case, well, I have no advice for you!
Happy new year, good luck with your choices, and I wish you years of joy playing whatever board you choose.
Again, a lot can be subjective. But also, take note of the date that was written, and the updates to the NS3 that have been made since then. That same poster posted this more recently...