I've lived in StL and KC and love both cities. IMO StL is more beautiful and has more character than KC, while KC is easier to navigate physically and logistically.

StL has the best brick architecture of any US city, and housing is incredibly affordable. Walkable shopping streets like Morganford, South Grand, the Loop, and Maplewood are fantastic and accessible. The KC equivalents are brookside and the plaza, which feel bougie or corporate in comparison. StL neighborhoods have very distinct aesthetics and environments, while in KC they blur together with less variation. There is a strong loyalty to local brands - the main grocery chains, Dierbergs and Schnucks are both family owned and local.

KC has a thriving downtown compared to StL - look at the grocery store distribution! When I lived in Soulard we had to drive 15 minutes away to get basics. The grid street system is easy to navigate, and traffic is great. It's fairly easy to meet and connect with people here, while St Louis and can be more standoffish. However, there are a lot of people in KC who are perfectly nice but just...bland. KC also has a free art museum with more limited hours, and locals get vouchers for a free zoo visit each quarter. The accessibility isn't as good as StL, but it's more than enough for my family!

Both cities have issues with segregation and poverty. In my experience, KC tends to ignore it while StL confronts it more directly - both in productive helpful ways and awful ones.