If we could not afford both GR4 and GR9 then one had to go as half of each would soon have gone tango uniform.
The better economic option was to cut the GR4 giving much greater savings.
From a military view OTOH there are more GR4 and their projected OSD is beyond the Harrier. If we had got rid og the GR4 and the JSF was late then we would have had a bomber gap down the road.
Clearly the military view prevailed and we at lest retain a half viable force. The point about the GR9 being capable of either AFG or Carrier but not both is well made.