Digg vs StumbleUpon vs Reddit

While Mashable was polling users on who would win the faceoff between Digg, StumbleUpon, or Reddit, gt1987 raised the point that each is unique and there need not be a winner.

I agree that each of these networks is very different. Here's what they mean to me:

• Digg is most popular of the three. With 20 millions monthly unique US visitors and 40 million worldwide, it's where I spend a fair amount of time.  It's about community working together as managing editor to decide what the best news of the day is.
• StumbleUpon is the place for viral content. It's lifespan is more evergreen.  I go there for random amusement or inspiration.
• Reddit represents the counterculture.  It's a place where memes emerge and thrive.

On paper, each of them is a community site where you vote up or down on a link, but as you can see, each is very different.