Is reinforced deflectors worth 3 points.

Or hull upgrade

i was looking at Tactical Jammer and running it with Wedge, gives you an extra dice against attacks as they have to target wedge so a bit of fancy flying can keep wedge in arc and possibility of a number of green dice.

In most games I would expect RD to save you more damage than Hull Upgrade, but RD has a much higher opportunity cost, in that the Systems slot is a very strong one, and taking RD costs you Accuracy Corrector, or Fire Control System.

(I wouldn't take Hull Upgrade either, by the by, depending on your build I might well leave the mod slot empty. 1 extra hull will make almost no difference to the Ghost)

Hull upgrade is probably not worth it seeing as the Ghost has zero agility and a pile of hull points already. Sensor Jammer or Reinforced Deflectors will both almost certainly provide more resilience but will use up the System Slot. Fire Control system is a great System upgrade, especially on a ship like the Ghost which has a powerful primary attack and can potentially attack with its turret as well.

If you want to keep the Ghost alive longer, I would be tempted to fly with Biggs as a wingman as he will soak up a couple of turn's shooting before he dies. You can boost this by giving him R4-D6 + IA, running Kanan as your Ghost pilot and giving the Ghost a Tactical Jammer to help boost Biggs' agility (situational but not bad for 1 point).

I tend to feel that the best defense is often a good offense so I would probably go for Fire Control System and ablative Biggs. Kill the enemy and he you will not have to worry about stopping him from killing you.