In my opinion, the 6-inch is more collectable since it represents the "original" Python introduced in 1955. Nickel is a scarce finish, so some will pay more for a nickel specimen, especially in the early production.
I like nickel but it’s hard to get,especially here in CA. None can be brought in from other states so what’s here is here
until someone decides to sell one privately. The price for nickel is about $1000 more then blue,all else being equal. So I wait.