FWIW, REI has a 25% off sale on all Giro and Bell helmets going right now. What carpediemracing mentioned is super relevant; depending on the environment and rider, there isn't going to be a clear winner.

I just switched to an air attack (still on the fence about appearance) from a giro savant. The savant is a traditional million holes design and has been fine, but the air attack is at least as cool with pretty much no sensation of air flowing through the helmet...which is kind of strange. More than that the air attack pretty much disappears on my head, which is fantastic.