It would be interesting to shoot the same subject with a Credo 50 and IQ250, same lens, camera etc. Hopefully the lighting could be controlled. I would be interested in outdoors.
Then open the files in C1, watch the files as C1 runs them, as they always pop a bit. Now load the default profiles Credo 50 for the Credo and IQ250 for the 250. Select two variants of each, and load the opposite profiles, i.e. load a IQ250 on the Credo and Credo on the 250.
I don't feel you will see much difference in the two. Unless Phase One/Leaf is still building a totally different controller card for the Credo which I don't think they are, the two images are going to be very close.
Just like you can take a D800e in C1 and load the default profile for the IQ250 on it. (At least you can in 7 I have not tried this in

, many in fact most times the C1 profile for the 250 looks better on the D800e than the default C1 Nikon profile.
Between the Credo 50 and IQ250, I am sure you can pixel peep between the 2, but I also feel I could get the file very very close in C1 without much work.
I also feel that Phase One is going to have the best raw conversion for the IQ250/credo 50, and for sure best noise to detail ratio. But I would also expect that.
Paul