The BTL-B is explicitly stated to be a different variant than the BTL-a4, as stated in the rebel starfighters owners workshop manual. There is a schematic in the book copied from an old legends source book that incorrectly implies they are the same, but the actual text of the book is abundantly clear they are different, distinct variants.
(btw im talking about the stock b wing's ion cannons, NOT the prototype beam weapon.) i want to talk about the utility of these two weapons, specifically when it pertains to the B wing. i had been wondering about the B wing and one of its main attractions are the ion cannons. It is described as being able to shred shields and subsystems. So my question is, what is the technological difference between ion and normal lasers? are they a lot more expensive than normal lasers? I always thought they were kind of interchangable, depending on preference/mission profile, but the lore about the ion weapons being so potent on the B wing almost suggests they are super expensive or hard to come by technology, because otherwise I dont know why you would ever use normal lasers when ion weapons seem much more versatile. or at least, as seen in skeleton crew, having 2 ion cannons and 2 laser cannons seems like the best combo. id love to hear everyones thoughts!
edit: also, that scene from Rebels with the Y wing using its ion turret interests me too, why is it depicted almost like a turret that shoots ion torpedoes, totally more powerful and different than the ways its depicted in games like squadrons and battlefront.