What is the main difference between swine flu and sars?

Viral type: The SARS illness was caused by a coronavirus and "swine flu" is the influenza subtype H1N1. Both result in a severe pneumonia and can result in multiple organ failure leading to death. The mortality rate of SARS was much higher than the pandemic H1N1, as was the propensity to spread via the air.

Different viruses: SARS is a viral respiratory illness caused by a coronavirus, or SARS-associated coronavirus. H3N2v is a non-human influenza virus that normally circulates in pigs and that has infected humans. Viruses that normally circulate in pigs are “swine influenza viruses.” When these viruses infect humans, they are termed “variant” viruses. In 2012, H3N2v outbreaks associated with exposure to pigs in July.