The Empire doesnt use the ships commonly flagged as rebelion because they either:
1. Cost too much to mass produce.
2. Arent efficient at what they do.
Let me give you an example of each:
1. The X-wing and B-wing are both topclass ships, but they cost way too much to produce, so the Empire goes for a cheaper Tie-fighter.
2. The defences on Hoth: they are really out of date. The Dish Cannon fires a Large bolt of Energy but 5 full shots expends the battery. Not to good really. 10 year old design roughy.
The Anti-infantry cannon (the big white one) also a 10 year old design taken from the imperials. Effective at what it does but its armour is too light to withstand even a light landing craft (ie scout AT-ST)
Now i know your gonna say "what about the Tie-Interceptor??".
The Tie-Interceptor is given to the most capebal pilots in the Fleet and are either sqadron leaders or higher in the fighter corps. They are not given the X-wing because a Tie-interceptor can easily out-turn one of them. The Tie-interceptor is only matched in speed by the A-wing, but as a result, the A-wings airframe and sheilds are very weak. True, the Tie interceptor is weaker, but it can out-turn an A-wing, but is slightly slower in speed. Twin Ion Engines have their limits you know.
