I’d say the Portal has a couple of things that the Horror doesn’t.
Firstly is Dread. An excellent addition to any army, but one I’m aware you can pick up relatively easily elsewhere in the Nightstalkers.
The other thing is it is a Scoring Unit, and one with De5 and -/16 Nerve. I can see it being a good Loot carrier and its Inspiring boost being limitless range means you can add US wherever needed.