Socialism has a record. Historically, it is the oldest economic system in the world and most prevalent. Free market economies are relatively rare. They both have records for all to see.
Socialism leads to economic collapse and political tyranny. Free markets lead to economic growth and prosperity for its citizens. The poorest citizens in free market economies live in in circumstances any socialist citizen could only dream of, other than the political elite.
Hitler Germany, Stalin's Soviet Union, and modern day Venezuela are the outstanding socialist models. We know how they turned out. The US, Britain, and the eastern half of today's China are the outstanding examples of free market models. Which of these would you have preferred to live in.
We know Bernie Sanders preferences. When married, he chose Moscow for his honeymoon at a time when Stalin's henchmen were still firmly in power. Certainly Sanders recognized what his goals were and what examples inspired him.