It is well known in manufacturing that a flow shop usually outperforms a job shop for comparable products. This paper aims to understand the impact of routing variability on WIP inventory, lead time, and delivery performance. A perfect flow shop has no routing variability, with every part following exactly the same sequence of processes. A job shop, on the other hand, often has significant routing variability. In reality, there can be any degree of variability, from the perfect flow shop to a perfectly random routing in a job shop, or anything in between. This paper compares the performance of a perfect flow shop with a perfectly random job shop, aiming to keep all other factors influencing the performance as comparable as possible. The goal is to isolate the impact of routing variability on system performance.