After all this time, Will, I hope you've been able to make your choice, but just cause I love leather helmets so much, I can't help adding my two cents.
I've owned and used on duty a Cairns N6A for 4 years, solid. Its a heavy helmet, but my neck got used to it. Our department does a lot of training so I wear it constantly. Its saved my noggin several times, acts like a shock absorber much more so than any plastic lined helmet. For looks, it sits deep on the head and I like that. The Paul Conway is tiny, sits high on the head, folks I know that have it have had trouble with their ratchets on the headband, and to be honest, it just doesn't have the old look to it that I prefer. There's really just something very kick ass about the Cairns leather, N5A or N6A.
Just my two cents. Leather Forever!!