Jeez - I'm slow.
I'm just about to make a decision, after months of tumbling my brain. Thanks to good help from friends on this forum, I decided to buy a used CZ 550 Magnum in 416 Rigby. And that gives me the opportunity, in a long run, to change the barrel to turn the 416 into a 450. And then two opportunities shows up - 450 Rigby and 450 Dakota. As far as I understand, the two are as good as one of a kind, both made from the basis of the 416 Rigby-case.
Then what is the practical difference, if any?
Does anyone of you have experience with these two calibers? I would love to peep into some tecnical drawings and ballistic data.