Here are three videos that demonstrate the differences between softboxes and umbrellas. The first is produced by B&H Photo.
You can see more videos like this on B&H’s youtube channel.
The next video is by The Studio Coach demonstrating the difference in the quality of the light from a softbox compared to an umbrella.
You can see more videos by The Studio Coach on his youtube channel.
The third video is by prophotolife describing differences between a softbox and an umbrella.
You can see more videos by prophotolife on his youtube channel.