defensive power (calculted in jets needed to break): turret = 1 tank = 2 troop = 0.5

in your example raw defensive power = 123

Weapons tech boosts defensive power

Defense bonus boosts defensive power

Dictator boosts defensive power 1.25x

Defensive allies boost defensive power up to 2x

For your example lets assume that you and your target have no weapons tech.
We will assume that neither you or your target is a Dict or Rep.
Let's also assume that your target has defensive allies that you are not going to spy.

Jets to send on a PS:
((2*123)/1.5)*1.1 = 180.4

Jets to send on a SS
(2*123)*1.1 = 270.6