Beatrice differs from Virgil in a number of ways. The most important difference is her beauty. Virgil is not a hottie with a body. Beatrice's beauty is strongly emphasized, but here's the cool thing: she uses her looks as a teaching tool. Since she grows more gorgeous with every step up the celestial ladder, Dante can't keep his eyes off her, and she uses his fascination to demonstrate how her perfected vision attracts more of God's grace.
Beatrice is—at times—an even more interminable teacher than Virgil. Her perfect knowledge can become tiresome. In particular, her put-downs of Dante's hypotheses can get on one's nerves. At times, the text threatens to turn into a long lecture. But, as it turns out, her infallibility helps Dante learn in leaps and bounds. Compare his pride and uncertainty in Canto II to the confident answers he later gives his three examiners. There's a world of difference there.
Did you notice that Dante always asks Beatrice for permission to speak before he actually does so? What's up with that? With Virgil, we saw some "Yes, sensei. No, sensei," but far less than occurs here. So why does Beatrice insist on it? The first and most obvious reason is that it keeps Dante in his place. Her authority over him reminds him that he's a student, there to learn, not to show off his scholarship. Notice that with Beatrice, Dante never gets quite as cocky and never talks back as he did with Virgil in Hell.
Second, Beatrice's authority allows her to regulate his speaking habits. Notice that half the time, Dante doesn't have to say anything for the souls to answer him, because they can read his mind. But when it isn't in Dante's best interest to answer something, Beatrice speaks for him—as in answer to St. James's first question on Dante's faith. It would look arrogant for Dante to go, "I've got hope, I've got lots of hope!" Beatrice gracefully intercepts the question and gives confirmation of Dante's strong hope. These subtle characteristics show that Beatrice is not only well-qualified to be Dante's guide, but also as skilful and compassionate as Virgil.
Given Beatrice's name, it's not surprising that she flashes those perfect white teeth so often. Her name comes from the Latin beatus meaning "blessed," and if we've learned nothing else from Paradiso, we know that all those in heaven are pretty happy with themselves. But Beatrice's frequent smile often indicates something other than just joy at being among God's favorites and hints at a rather enduring trait which her male counterparts don't have. Let's knock around some possibilities.
The first thing that Dante always notes about Beatrice is her beauty. And this is no doubt enhanced by her smile. As we've discussed earlier, the power of her smile increases with the brightness of her soul the higher she ascends into Heaven. Each time our two heroes ascend into a new sphere, it seems like Beatrice's smile gets bigger and brighter. And more often then not, Dante goes into poetic rapture about how gorgeous she looks and how he cannot possibly capture her beauty in words. Here, the increasing dazzle-power of her smile seems to reflect a simple love for God and growing joyousness at drawing nearer to him. His love shines through her smile and eyes at Dante, conveying the infinite compassion God has for all his blessed.
We've grown so accustomed to her brilliant smile that it hits us like a bucket of cold water when she doesn't smile. That happens in Canto XXI when they've ascended to Saturn. Her explanation? She's not displeased so much as she's looking out for Dante, because up here the dazzle-factor of her smile would burn Dante's eyes into blindness. So she goes without smile for a while, until Dante has witnessed the re-ascent of Christ and Mary into the Empyrean. After seeing so grand a sight, Dante can withstand her beaming, so she bestows it on him again in Canto XXIII. The purpose of these smiles, it seems, is to reflect the love of God.
Then there are times when Beatrice has just a wisp of a smile of her face. And these instances almost always accompany one of Dante's (spoken or unspoken) questions. This smile says, "I know something you don't know." We like to call it her knowing smile, but we've heard it referred to as "Merlin's smile," a popular medieval motif that occurs when some character has foresight or more knowledge than another and is amused by his or her haplessness. Which sounds exactly like the relationship Beatrice has with Dante.
Beatrice's' playful, knowing smile appears a number of times: right after Justinian's long discussion on Roman history when Dante has questions about the justice of Christ's crucifixion; right after Dante's learns that Cacciaguida is his great-uncle; and when Dante is having a proud moment over his noble ancestors.
This last example is a particularly playful moment. While Dante's head swells to the size of a melon, Beatrice quietly stands aside like a knowing mother, smiling and shaking her head. She's amused. That's right, she's gently mocking Dante for being such a fool. And we know that because it's compared to "the woman who had coughed… at Guinevere's first fault." So Beatrice's ironic smile points out Dante's pompousness (his "first fault"), hints at how ridiculous it is, and subtly laughs at it.
We have a theory that Beatrice's smile is contagious. We swear it spreads. In Canto XXII, Dante looks down on the Earth and smiles scornfully at its pettiness. In Canto XXXIII, St. Bernard smiles at Dante when the Virgin Mary accepts his prayer. And in Canto XXVII, the whole universe smiles. What's up with that?
Here's our final theory: Beatrice's smile captures the whole of Heaven's attitude towards mankind. God, the angels, and the blessed know they're morally superior and more knowledgeable than man; they occasionally find entertainment in man's foolishness, but it's all in good fun. The important thing is that they're affectionate towards mortals; ultimately they have only goodwill toward them.