the reason to keep enterprise structure easy and simple is mainly for the sake of maintaining master data. as we know in sd there is customer master, material master, condition master, output master, etc. among which customer master and material master probably counts most. let's say if you have the same customers and products for two segments, then defining two sales orgs means you will always have to create your master data twice, in both sales areas. Even if some customers are not inter-usable, you can always common distribution channel.
If you already maintain different customers, then you might wanna look from the standpoint of material master. pricing strategy.