I use both! Black Numenoreans in front with Morannon spear support, providing a nice F4 S4 battleline
I'm a real fan of Black Numenoreans (mostly because of their look and storyline), no seriously I never leave without my 12 babies
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But gaming wise I'd say Morannons. BNW have a really hard time killing stuff due to their S3. That combined with not having Fury is a real bummer. D6 with 5+ fury is just too nice.
Also, these days you're either facing high courage Good or Fury affected Evil which means Terror has less use now.
Tournaments in my neighbourhood are swarmed by Goblin armies so F3 isn't really that much of a problem.
Their price in money is something to consider too ofcourse. Happy I bought mine when they were still metal...