Additional Study Information: The purpose of this study is to compare the efficacy and safety of two standard-of-care drugs, Risankizumab (Skyrizi) versus Vedolizumab (Entyvio), over 48 weeks to compare how well these drugs work in patients with moderate to severe Ulcerative Colitis (UC). This study is being conducted at approximately 285 research centers worldwide and is expected to enroll approximately 530 patients in total with moderately to severely active UC. Your study participation could be up to approximately 69 weeks if you are assigned to the risankizumab group or up to 71 weeks if you are assigned to the vedolizumab group. This includes up to a 35-day screening period followed by a primary treatment period of 44 weeks for risankizumab and 46 weeks for vedolizumab, and a 140-day follow-up call after the last dose of study drug. The only difference in this study is that you will be randomly assigned (like flipping a coin) to receive either risankizumab or vedolizumab. The dose you get will be the same as what you would receive if your doctor prescribed the medication outside of the study.