Shea argues that Barron is saying almost exactly what Pope Benedict XVI said on the topic, whereas Windsor argues that Barron's position comes close to falling under the condemnation of the Second Council of Constantinople. Per Windsor, Barron's view is "scandalous at best and perhaps even heretical" whereas Shea thinks "Barron is guilty of no heresy, has said nothing “wrong” and is perfectly within the pale of orthodox speculation."
At issue is Barron's apparent view (which he says agrees with Balthazar's view) we should believe that Hell is at least possible (as a metaphor for loneliness from divine love, not actually a place) but that we can reasonably hope that Hell is empty based on God's universal salvific desire. Barron concedes to the big tent nature of Roman Catholicism, pointing out that folks like Augustine and Thomas Aquinas would disagree with him.
Shea likewise balances his comment by pointing out:
Now those, such as Ralph Martin who speculate that few will be saved are also (obviously) also within the pale of orthodoxy and share their opinion with not a few Fathers and theologians. But at the end of the day, that’s all you have: two schools of opinion–both of which are allowed by the Church.But it's not just Windsor and Voris vs. Shea and Barron. We could add that we have previously pointed out contemporary cardinals holding that hell may be empty (Cardinal George Pell and Cardinal Cormac Murphy O'Connor).
So, what's the big deal? Well, on the one hand - the Scriptures are clear that there will be men in hell. For example:
Matthew 7:23And we could on and on. Although the great Origen erred in hoping for the eventual restoration of all creation, such a view is not consistent with Scripture's teachings both that hell is real and that the punishment of hell is eternal punishment.
And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.
Then shall he say also unto them on the left hand, Depart from me, ye cursed, into everlasting fire, prepared for the devil and his angels:
And death and hell were cast into the lake of fire. This is the second death.
But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death.
For many are called, but few are chosen.
1 Corinthians 1:26
For ye see your calling, brethren, how that not many wise men after the flesh, not many mighty, not many noble, are called:
For this is my blood of the new testament, which is shed for many for the remission of sins.
And he said unto them, This is my blood of the new testament, which is shed for many.
What if God, willing to shew his wrath, and to make his power known, endured with much longsuffering the vessels of wrath fitted to destruction:
But the children of the kingdom shall be cast out into outer darkness: there shall be weeping and gnashing of teeth.
So, on the one hand, Windsor is right that people like Barron and a couple of Windsor's cardinals are wrong. On the other hand, such a problem is not resolvable on Roman Catholic grounds for basically the reasons that Shea and Barron enunciate: there has been no "official teaching" that anathematizes one or the other position, and consequently both contradictory positions are acceptable, even though both cannot be right.
Worse yet for Windsor and Voris, the evidence is that the current hierarchy supports and teaches the erroneous view. I have not confirmed whether Shea is accurate in characterizing the teachings of Benedict XVI, but it clearly extends at least up to the cardinals.
The most remarkably thing is that Windsor and Voris continue to trust in this church (which teaches and promotes errors that they themselves are able to identify) rather than trusting in God alone and His Word. They may be able to convince themselves that these same hierarchs would never commit their erroneous doctrines to an allegedly infallible document, but such thinking seems wishful indeed in view of the highly compromised documents of Vatican II, not to mention the victory of the ultramontanists in Vatican I.