In "Stopping by Woods on a Snowy Evening," what are the snow flakes compared to in the poem?

The adjective "downy" does seem to suggest that the
snowflakes are being compared to "down," which is defined as a noun meaning the soft,
first plumage of many young birds or the soft under-plumage of birds. The word "downy"
in this sense would mean "down-like." Goose down is commonly used for stuffing pillows
and comforters. Eiderdown, the soft feathers from the breast of the female eider duck,
is especially prized for such purposes. The ducks pull the feathers out of their breasts
to make nests in breeding season, and humans will gather these nests to sell for very
good prices.

The word "downy" also might have been intended
to suggest the idea of "falling," or moving downwards, which can be felt throughout the
poem, especially in its seemingly downward-trending rhyme scheme. The AABA rhyme scheme
in the first stanza becomes BBCB in the next. The B in the first stanza is picked up and
continues falling throughout the second stanza, and so on. But the main comparison seems
to be between softly falling, extremely light snowflakes and the white down of
birds.

If we wanted to stretch this comparison further, we
might say that the word "downy" suggests that the speaker, sitting there in the cold, is
thinking of his own warm bed with a down-filled comforter and a down-filled
pillow.