Interesting that the two leading options represent such diametrically opposed philosophies. People really took the devil's advocacy to heart, huh? Honing is a fine option too, you know. Not as fine as it would've been if we had Threefold Wits to convert into combat-specific Int, but still quite solid, Agility's good for us. If we pick up every shiny on the road to Once and Future it and the associated Forebear lore will recede forever into the distance, a carrot dangling just beyond Hunger's reach.
But between the Vanquisher's Halo and Skyveil? It isn't even a question. The Veil provides +5 Protection, but consider that the Halo's +5 Charisma also increases Protection. Thanks, Vigor Incarnate! What an amazingly efficient advancement you are, isn't it great when we can straightforwardly improve the value of a stat, now and for all future increases? And here we are, being offered the same deal again. Strength's even better than Protection since it improves the Power of Ruin, soon to be a Keystone of our build once we pick up All-Defeating. Removing Uttermost's malus is effectively a 30% efficiency boost to Charisma, but aesthetically more pleasing because we're excising a tumor of inefficiency from our build, paring away a weakness on Hunger's character sheet.
But ultimately, this comes down to one thing: I would rather confront problems caused by being too strong, than ones caused by a lack of strength. That's true both socially and physically; we shouldn't discount the risk we chose to undertake just because of recent successes. We're walking into danger, and the Vanquisher Halo is just... flat-out better than Skyveil in battle, full-stop. There's basically no way to argue otherwise, the only thing Skyveil has an edge in is Agility, but the massive Power of Ruin increase and social offense more than outweighs it. Vanquishing is literally in its name! There are some merits to enabling a stealthy approach, but recall that Hunger has already committed to not doing that; Tower Itself won, he's going to be making straight for the Tyrant's lair in hopes of avoiding Decimation uptime after tarrying in the Sovereignty. Also, our task is to topple the Tower. Maximizing the of Power of Ruin would be invaluable for such an endeavor.
Besides, don't you guys want to keep pace with Gisena in the Charisma arms race? Teasing is a two-way street, or at least it should be!