Both are sculptures created by Michelangelo that deal with historical subjects. However, Victory deals with the depiction of the religious story of David and Goliath and Bacchus is the mythological representation of the god of wine. Both works also deal with key beliefs in the Renaissance. David was symbolic of Florentine civic humanism and virtue, ”Michelangelo’s loyalty to the Florentine Republic meant that he became involved in producing heroic Republican imagery,” the story of David overcoming Goliath symbolizing good versus evil was a common theme. The representation of Bacchus was an attempt to fuse the Pagan and Christian religions together in Neo-Platonism, another common theme within the Renaissance.
David’s head in Victory is crowned with laurel leaves, symbolic of victory and of the Medici family. The panther or lion skin that Bacchus is holding is representative of the story of Bacchus or Dionysus (as he is also known) who was also believed to be the god of the cats. In Roman mythology, Bacchus was the God of wine, intoxication and madness. Many of the miracles later ascribed to Jesus were first performed by Bacchus, including turning water into wine and a miraculous resurrection.
Bacchus was made for Cardinal Riario, Michelangelo’s first Roman patron. Bacchus is a young man in a contra postal stance. Leonardo may have influenced Michelangelo with one of his studies, St. Sebastian, in the creation of the Satyr behind Bacchus. The study shows the reverse positioning of the Satyr, but has the same turning and twisting of the body that will become greater as the movement from High Renaissance develops to Mannerism. Michelangelo’s Victory is very similar to Donatello’s David in marble in 1408. This twisting and turning movement is fully realized in Victory.
Both sculptures are depicted on the artist's conception of physical perfection as opposed to the portrayal of a particular person. Bacchus was created in the classical tradition of High Renaissance sculpture. Michelangelo was very concerned with the classical tradition. His depiction of an idealized view of beauty of the human body, contra postal stance, and naturalistic pose, albeit one of drunkenness, is a classical representation of Italian Renaissance style during the Cinquecento. His ability to model his sculpture after the ancient works of Greece and Rome was largely due to his proximity and ability to study works owned by the Medici.
Victory is credited by John Shearman for being the first evidence of the figura serpentinata, one of the characteristic forms of the Mannerist style. Although he didn’t invent the serpentine movement, Michelangelo did investigate gestures and movements by dissecting corpses in the Hospital of Santo Spirito, hoping to author a treatise on anatomy for artists. The twisting and turning of the body of David in ways not possible in human form and his elongated limbs were a new style and a prelude to Mannerism. Michelangelo also influenced artists with his Victory sculpture like Andrea del Sarto who drew from it when creating his painting Sacrifice of Abraham.
The movement of the two figures differs in that in Bacchus there is an almost unbalanced, uneasy movement of the figure alluding to his drunkenness. One is encouraged to walk around the work to see the satyr behind. In Victory, the movement is much more of a vertical spiraling movement, a hallmark of the Mannerist style.
Both works are worth a look if you can find the images online. You will notice a difference in these sculptures and earlier Renaissance works.