Cabinet Art: Both look great.
PF Art: Iron Maiden by a mile. The art isn't only beautiful, it's true to the band. Keith's Iron Maiden podcast (http://www.podcastgarden.com/episode/episode-242_125160) pointed out the great collaboration between the artist and band. I know some rabid Iron Maiden fans and they LOVE what they see. I grew up with both bands and have seen both Alice/Iron Maiden live. I'm a much bigger Alice Cooper fan and was pretty disappointed by the lack of Alice imagery on the Spooky PF (not talking about his "mug"...more about symbols from his albums and stage show).
PF Layout: Iron Maiden by a mile. The Iron Maiden PF looks long, fast, and the ball is much more visible throughout the entire PF. The Alice PF looks shortened and slow by comparison (upper PF, castle). Most players I know don't like when the ball gets obscured too much.
Rules: No clue, but have to give the edge to Iron Maiden (Keith Elwin is likely to develop rules that will keep us busy for awhile!).
LCD images, callouts: Who knows? (haven't seen much detail yet). Wouldn't be surprised if ACNC wins on this point. I hear there are tons of Alice callouts, but have limited info. As Keith points out on the podcast, fancy imagery is for the observer...not the player. Keith's pin will be player-centric, for sure.
From my perspective, ACNC looks like a haunted castle pin with Alice Cooper as the main character. Not an Alice Cooper tribute pin, per se. I understand this was "by design" and will appeal to folks more interested in a haunted castle pin with some cool callouts and music by Alice Cooper.
To be honest, I wasn't paying much attention to Iron Maiden pinball, but the PF art/layout looks amazing and I'm sure Keith will make sure the rules rock.