You probably noticed that in Paragraph A is easier to understand.
The ideas flow logically from sentence to sentence so that the reader can follow them easily. In other words, the transition from sentence to sentence is clear. However, In paragraph B, the ideas do not flow logically and the reader has difficulty reading from sentence to sentence.
Another way of explaining the difference between the paragraphs is that paragraph A uses given and new information more successfully than paragraph B. It also chooses the main subject and verb in a logical way and presents it clearly to the reader.