According to the St. Louis Fed, GDP is about $188 billion for the St. Louis MSA, and $155 billion for the Kansas City MSA. A 22% difference. That's with a fairly significant difference in population. 2.2 million to 2.8 million. 27% higher population in St. Louis. Recent population count has St. Louis MSA declining slightly in population, Kansas City MSA increasing slightly.
https://fred.stlouisfed.org/series/NGMP41180
https://en.wikipedia.org/wiki/Metropolitan_statistical_area
St. Louis is the older city. St. Louis city proper recently dropped below 300,000 for the first time since the 1860's, down to 296,262. Kansas City proper is still growing. Recent population 522,580, an all-time high.
https://worldpopulationreview.com/us-cities/st-louis-mo-population
I want both cities to do well. I grew up in one area and currently live in the other.
Columbia's city population has more than doubled since I was a student. currently 131,579.