Okay so squadron packs, they are 3 ships, 1 pair and a single ship. The thing is that squadron packs have 1 ship you can't get in another expansion. However it is likely that the expansion that has the other ship that is not unique to the squadron packs will have some upgrades not in the squadron pack, just as the squadron pack will have upgrades that are not in any other expansion released up to Wave 3.
So basically you need to decide what ship you want. If it is the one that is exclusively in the squadron pack, plan on picking one up. If it is the one that is in the squadron pack and has an expansion, you are likely going too have to get both. If it is not in the squadron pack, you could get away with not grabbing one. However with the 3rd wave factions only having 3 ships each, it is unlikely you are going to be running a list of all Sith Infiltrators or ARC-170s.
Edited by Marinealver