Common stock is easier to buy and fluctuates in price more. Preferred stock has a few differences. Preferred stock typically pays a higher dividend than common stock. Because it pays out a larger dividend, the price of the preferred stock is less volatile. So if XYZ Corp announced a hot new product, the common stock might soar but the preferred shares wouldn't react as much.
Some people choose to own preferred stock over common stock for a few reasons.
Some like the idea that they can earn a much higher dividend. Others like that they are less volatile and if the company goes bankrupt, a preferred shareholder is more far more likely to get at least some of their money back, making the investment much less risky. Also, people with a lot of money invested in a company sometimes like to own preferred stock because it typically gives them more voting power than someone who owns the same amount of common stock. Although preferred stock has its benefits, common stock is probably best for the average investor like you and I because it is easy to buy and earns a higher rate of return. But it's always good to understand all aspects of investing.