What is the difference between slugs and pellets for the Winchester?

I think the pellets can kill more than one zombie per shot, if you get the shot right. The slugs have more stopping power and no spread, so they're better for range. Also, I believe they're reducing the power of the 'winnie' so pellets might not be up to the task of one shotting zombies any more.

From the DayZ wiki:

Slugs are solid rounds for shotguns that have decent range and stopping power. Pellets are rounds of buckshot that spread out at short range (about a quarter of the range of slugs). Pellets are more situational, and are probably only superior to slugs in buildings.