Swallows or Snails?

The latest edition of The New York Review of Books has an essay on Proust by Andre Aciman. He begins by classifying novelists into two categories - Swallows and Snails:

We'll say there are two kinds of novelists: the snail and the swallow. The swallow is quick, agile, and able to speed across long, tireless stretches. Nothing a swallow does goes wrong; mistaken turns are instantly corrected, bad weather is put to good use, and poor judgment can be tweaked just enough to look like a flash of genius. In the implacable assembly line of prose, nothing is ever wasted or thrown away. By contrast, the snail is slow, deliberate, fussy, cramped. Swallows travel and seek out the world; the snail burrows into itself. The swallow acts; the snail retracts, guesses, speculates. A swallow chugs life down the way whales take in water, plankton and all, while the snail ingests choice bits down a multichambered spiral, where its appetite, like its vision, is eternally whorled. Balzac, Dickens, and Fielding are swallows, even Tolstoy.

I am not sure, if I understand what he means. But later, he says Proust, Gogol and Stendhal come under the category of snails. Well, that pretty much decides for me, as to which camp I belong to!