It depends how long you intend to keep it. My Dad's car was recently repaired as Cat D which took a significant amount off the trade-in value, and the car is probably in better condition than before the repair.
Also as of the start of this month the categories have changed and C and D have become S and N:
A: Scrap
B: Break
S: Structurally damaged repairable
N: Non-structurally damaged repairable