Crown and shape performance has been one of the most important technical and quality subjects focused by metal producers, mill designers, and rolling researchers. For past decades, many crown/shape control devices have been innovated and applied to mill operation in the metal industry. And numerous crown/shape mathematical models were developed in the literature to predict crown/shape performance for various mill configurations and product mixes. This article compares the crown performance of vertical stack mills (4-hi and 6-hi) using typical 4-hi and 6-hi mills with various strip widths and moduli. The results were calculated using a crown/shape model based on the bi-directional two-stage transport matrix method, which emulates the mill as a spring-beam-gap mechanical system. Natural crowns (generated by separation force) are calculated first as the crown disturbance to the mill. The crown effects of both mills due to incoming crowns, roll crowns, roll bending, roll shifting are calculated to reveal the linear crown control characteristics of the mill. Roll shifting effects are linear approximately in the 4-hi mill, but are not quite linear for the 6-hi mill, particularly, mid-width and low modulus strip. The quadratic and quadric crown components of natural crowns, roll bending effects, and roll shifting effects are also discussed in the article.