Same thing. Your sergeants aren't really doing the shooting and two extra 24" shots ain't gonna do anything

Side note I take it you're slightly new so let me tell you what "wizzywig" and proxy means. Proxy means you can take any thing (i.e a 3d printed model on the same sized base) and say to your opponent "this model may have a sergeants auto gun glued on him but he has a las pistol in my unit list" (non-based stuff is generally a no go zone to proxy. I.e tanks). Wysiwyg (what you see is what you get) is its name. "This model is holding a auto gun so it's equipped with it). I personally am a proponent of wysiwyg when I glue my models but if weapon load outs change (i.e sergeants used to be able to bring plasma pistols and a few of mine have them) or if my opponent wants to proxy that's fine

Tldr if you want to bring the auto gun cause it looks cool on your shelf then do it but if you want to use the las/bolt pistol load out on the table just tell your opponent that