Hi Mike,
It depends if you need a car or not, we use Gib when we are staying in Duquesa/Sab and walk, bus or Taxi locally, car hire is available in Duquesa but we have not used it.
The advantage of Gib is that it is closer and you just turn right out of the arrivals walk over the border and you will find a taxi rank on the right (or get mates to pick you up). I think we paid about 40 euros last time for a taxi.
A word of warning, there have been occasions in the past where Spain has closed the border!!! I dont think this has happened for a few years but??
When we need a vehicle on holiday we usually fly into Malaga as prices are more competative
Hope this helps