This post is from my book Creative Synergy.

During the Italian Renaissance it was common to debate the merits of painting vs. sculpture. We tend to lump them together as visual arts, and they do require somewhat similar skills, but there are significant differences. For one thing, a painting is executed on a flat surface, and a sculpture is usually viewed from all angles. Michelangelo’s David makes an impact from every point at which the viewer stands; and, in fact, observers are encouraged to walk slowly around him, viewing the perfection of his buttocks, the veins in his arms, the musculature of his legs. The impulse to touch, almost irresistible, is restrained because the lower part of the statue is surrounded by a small fence. (What amused me as I gawked at the David is that many spectators, eschewing the statue itself, were crowded around a digital showcase of it, viewing as if hypnotized the rotating images expressing its different views. So mediated have some of us become that we cannot, as was once said of Newton, “look on beauty and see it whole.”)

At any rate, the talents required of sculpting and painting are different. The sculptor, especially in earlier eras, had to be strong and work with physically challenging materials, which were often quite expensive. A painter can cover a mistake, but a sculptor can ruin a block of marble with one wrong blow.

During the early fifteenth century, the rivalry between Leonardo and Michelangelo sometimes manifested as a debate about which was the better art, sculpting or painting. Ross King has an engaging account:

The surly Michelangelo had once taunted Leonardo in public for having failed in his attempt to cast a giant bronze equestrian statue in Milan. Leonardo, meanwhile, had made it clear that he had little regard for sculptors. “This is a most mechanical exercise,” he once wrote, “accompanied many times with a great deal of sweat.” He further claimed that sculptors, covered in marble dust, looked like bakers, and that their homes were both noisy and filthy, in contrast to the more elegant abodes of painters (King, pp. 23-24).

When Pope Julius II commanded Michelangelo to paint the ceiling of the Sistine Chapel, he agreed reluctantly; though once apprenticed to a painter, he had had little experience with a brush and considered himself a sculptor. In particular, he had had no experience at all with fresco, a demanding technique that required painting on fresh plaster (King, pp.22-23). Leonardo himself had failed with fresco while trying a new technique in The Last Supper (1495-1498), which had already disintegrated to what Vasari called “a glaring spot” seventy years later. Leonardo’s desire for innovation had caused him to reject the technique of “buon fresco” and paint “in tempura and oil,” which he could do in his own “erratic rhythm” (Pedretti, p. 188) rather than being forced to work quickly while the plaster was wet.

References:

King, R. (2003.) Michelangelo and the pope’s ceiling. NY: Walker.
Pedretti, C. (2005.) Leonardo da Vinci: Artist, scientist, inventor. Florence-Milan: Giunti.