If this were the case with ANY of the factions, I would agree. It isn't.
The NPC factions of Disco should stay around, they have established story lines, NPCs, Bases, etc.
As far as benefits, we've all gone over this 1,000x so I won't argue it again. If you have an indie trader, cool, keep him. If you want some interesting RP though, hop on one of the less active trading factions and enjoy all sorts of different interactions in them. It's really worth it.