I'll give it a shot first by saying to you that I would not be fearful of buying any used Genzler or Genz Benz gear. It is that well made and backed by two men (Jeff Genzler and Andy Field) who post here almost daily. Andy still handle repairs and much of the older Genz Benz gear keeping it in operation for those owners.
I believe by reading about them on the Genzler site you can get answers to your questions about the differences but safe to say that NuClassic cabs have a more traditional ported cabinet design using ceramic magnet drivers coupled with a compression tweeter. But they are also very lightweight. I'd say the name says it all. They're a more modern and efficient approach to a classic bass cab design.
The Bass Array cabs are a much different concept in cab design. The Neo drivers handle only the lows and low mids allowing the vertically mounted speaker array to handle the mids and the high end each doing what they are best at in the frequency spectrum. What they produce is a very transparent uncolored tonal picture of what each bass sounds like. They're a great match for any of the Genzler bass amps.
Another feature is their off axis sound dispersion. You don't lose anything if you're standing somewhere other than directly in front of the cabs. The effect is much the same as you get with PA systems which also use a speaker array design. Which cabs will work best for you I can't honestly say but I love the design and advantages of the Bass Array cabs. They are also very lightweight. Play each of them if you can.
