A cold is a milder respiratory illness than the flu. While cold symptoms can make you feel bad for a few days, flu symptoms can make you feel quite ill for a few days to weeks. The flu can also result in serious health problems such as pneumonia and hospitalizations.lu symptoms are usually more severe than cold symptoms and come on quickly. Symptoms of flu include sore throat, fever, headache, muscle aches and soreness, congestion, and cough.