IMO, the black version of the Nimbus is better but there's plenty of personal preference involved. The crossover requirements are different with Accuton requiring a steeper slope to avoid the nasty breakup peaks while the Audiotechnology driver can use a shallower slope and it blends perfectly where the Accuton doesn't quite blend as smoothly. I know Ryan at Vapor would also agree, unless he's figured out how to get the Accutons to behave a bit better. They may have done so after developing the Perfect Storm, the Accutons used on the PS did sound quite a bit better than I remember in the Joule or Nimbus, so that may have trickled down... Also, many mfg'ers are figuring out the Accuton drivers are best modified with some damping material on the backside of the cones, so it's possible Vapor has also made some progress in that area.
If you go with Vapor you can customize quite a bit, I might go with the Joule's mid/tweeter arrangement on the Nimbus instead. But be prepared to wait...
For me it would come down to Vapor, JBL or TAD... and with TAD being so expensive, IDK... the CR-1s mid/tweeter is amazing but the Vapor and JBL have really nice 15" woofers. The TAD Ref-1 has plenty of woofer but it's double the price of the CR-1.
That's the beauty of using the Accuton dome mid with the midwoofer. You can cross it over lower, and have a seamless blend into the midrange. Let alone one of the most holographic midranges possible. Accuton driver's are well suited for the very finest active designs. Audio technology drivers are excellent for passive 2, 2.5 ways.