I haven't hear either sub but do have an NSD driver in my 16-46 cylinder SVS. As the largest cylinder it is excellent for films and organ music in particular. It offers effortless power which easily shakes the whole house on LFE.
With its larger box the NSD should offer greater bottom end extension and a greater sense of effortless power over the SB12+.
The SB12+ will probably sound more tuneful and "quick" on music.
But if you're a film fan then choose the NSD.
If you're really a music fan then the SB12+ arguably a better choice.
If you have a small room then the SB12+ will offer greater flexibility in positioning for obtaining the best performance.
The PB12NSD is probably a slightly higher tune than my big cylinder so should offer even greater output with only marginally less extension into the infrasonic region. Do you need this level of performance?
If you live in a flat or semi I would choose the smaller SB12+ to help limit annoyance to the neighbours.
If you have no close neighbours then go for the NSD and have a total blast. I cannot imagine anybody (normal) wanting more power than I get on action films from my sub. WOTW when the machine emerges is an unbelievable experience. With everything shaking wildly it sounds like my house is literally being torn apart.
Enjoy your choice whichever it is.
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