I am very partial to 45-70s and I don't have any first hand knowledge of the 450 marlin. My main purpose will be deer hunting and fun I do reload for the 45-70.
Pretty much answered your own question there. The 450 Marlin is nothing more than a hot-loaded 45-70 wearing a different case. I really don't think there is room for it and the 45-70 in the world and since the 45-70 s here to stay....