Another angle: (excuse pun)
Rate of turn is degrees per second.
Radius of turn can be relative to the ground eg if you configure slow safe cruise and turn at about 45 degrees angle of bank into wind, you can do a 180 without covering much, or any, ground. For the same reason at low level or in a valley you should always turn into wind, reduces the radius of turn in terms of distance travelled as well as reducing the liklihood of getting disorientated.