Generally, every fighter in the list has the same starting equipment.
Where this is not the case, promotion works differently. For example a Chaos Cultist that becomes a Trooper does not become a CSM and a Necron Warrior that becomes a Trooper does not become a Necron Immortal.
Craftworld Eldar are the exception to the exception. Guardians promoted to Troopers become Dire Avengers. They lose Mesh armor and gain Aspect armor - they also lose their ranged weapons and gain a single Avenger shuriken catapult.