Redundant Weapons?

[MeChANiClySM]

I've been following KT a long time but I can't seem to find a simple reason for why some weapons appear redundant or are objectively worse. I am not talking about the difference between high volume of attack weapons versus power or plasma weapons. I am talking about weapons where there are 2 different weapon options (usually for sergeants) that have the same number of attacks, same BS/WS, same damage, and have identical special rules.

 

Example: The Kasrkin Sergeant can be equipped with either "Bolt pistol; power weapon" or "Hot-shot laspistol; power weapon". Both the Bolt Pistol and Hot-Shot Laspistol have identical profiles, 4, 3+, 3/4, Range 6. But the Hot-shot laspistol can take advantage of a ploy for hot-shot weapons...what is the Bolt Pistol for?

 

I've seen a few like this but this was the one that brought me here searching for answers. The only answer I've heard so far is so that 40k models are compatible...

[Tonius]

I think it is maybe so that you can play KT with minis from your Wh40k army, without having to build/buy KT specific ones.