For BGs, I can definitely see Okoye being the top; since her damage is almost certainly higher.But since you asked about overall content, Chee'ilth's Utility takes the win, at least for me: Grit to (passively) counter Unstoppable feels more valuable to me than Ensnared is (as a debuff) to counter EvadeCleanse is way better than EnduranceTranquilise + Cleanse almost makes for full debuff immunity, played carefullySustainable Miss counterSolid Regeneration on SP3Sig ability counters physical burst effects (Whiplash, Traumas, Ruptures)
Let us know which one you choose and if you end up backing your decision!