Erianas Vow not a HC?

So I bought this gun from the kiosk hoping to shot two birds with one stone in the NFs. Then I realised that this gun uses special ammo and on top of that HC unstoppable mod doesn't work with it. Now comes the big question, why should I chose this gun over let's say riskrunner or just Ikelos SMG or some other puls rifle?

Another question, do all the other armor HC mods work with it?