Downy vs. Hairy Woodpecker, can you tell the difference?

Downy Woodpecker, m. (left), Hairy Woodpecker, f. (right) on Stokes Select Four Cake Suet Buffet feeder.

Wow, look at the size difference. In this photo you can see the bars on the outer tail feathers of the Downy Woodpecker. This usually occurs on most subspecies of Downy Woodpecker except the "leucurus subspp (s.e. AK-. NE south to AZ-NM) may lack barring on tail." (from The Stokes Field Guide to the Birds of North America, which contains information on all subspecies of birds, no other field guide does). The Hairy Woodpecker usually has white unbarred outer tail feathers (except in a few subspecies).