There is no crash test difference between either the KF or the SR22. They are both perfectly safe seats.
If you came into a check and asked my opinion, I would tell you to use the SR for the first couple of months then put the baby in the Radian (which fits infants well). You could then use the money you "save" on not buying an infant seat and purchase another RN. You'll be needing four convertibles eventually (2 for each vehicle).