If they are not a super early push button door handle I am not sure if there is a real difference in price between 71 to 74. It will depend on a few main preferences and then how well the car is restored either stock or modified to a buyers taste. Some will only ever look at small bumper Pre L's others prefer the single pod dash found in 73 and 74's. If the cars are stock then some may search for a late serial number (usually tagged as 74's) to get all of the factory updates done for Ford.
If the car has sat for a long period and needs to be completely gone through I don't think there is a price difference. They are all getting older and they will all deteriorate and rust if not taken care of.
Buy the best possible car you can afford. A beautiful 72 just sold for $88K on Bringatrailer. "Fixer Uppers" in Pantera's will require more financial means than doing a Mustang or Camaro.