Both single stage and two stage snow blowers both have the end goal of removing snow but accomplish this in different ways.
Single Stage - A single stage blower used a paddle system to scoop the snow and throw it out the discharge chute in one motion (or stage)
Pros: Clear snow to the pavement, light weight for transportation, compact for storage space, very efficient at removing small amounts of fresh snow, paddle system helps assist the blower along.
Cons: Cannot be used on gravel drives, not efficient at moving large amounts of snow, limited sizes available, paddles and scrapper bars need replace after 2-3 years.
Two Stage - A two stage blower has a metal auger system (first stage) with serrated teethto break down the snow and an impeller (second stage) to throw the snow out the discharge chute.
Pros: Can be used on gravel drives, can fight through large amounts of snow fall, have wheel driven self propel, large sizes available
Cons: Heavy and tough to maneuver, not proficient at removing small amounts of snow fall, take up more storage space