Ya know, a lot of people swear by nitro. All I can say from a user standpoint is - I have a lot of nitro basses and a lot of poly basses, and even a CA bass, some mineral oil basses and even a bass body sprayed in truck bed liner material. Darned if I can hear any differences in them that I can attribute to the finish. Some of my best players are poly. As long as the neck isn't grippy or tacky I'm a happy camper. One thing you can say about poly is its durable.
BTW - your refins look fantastic! I'm still on the fence with a JC Hollowbody, does it get a lot of feedback at stage volumes?