Both are low distance spray weapons.
At the moment though, the shotgun seems really weak compared to the flamers.
Flamers do more damage and additionally set on fire.
I think, shotguns would need an additional benefit which makes them also feel more like a shotgun.
Maybe a trait that makes more damage or on thenwound table on point blank ?
"If the target is no more than 3m away, this weapons does +5 on the wound table, if the target is wounded"
That wouldnt be too bad for a shotgun and underline its use in narrow space and against closing up opponents.