Not which city is better
Kyoto and Osaka are close, but they do different jobs. Kyoto gives culture and early temple days; Osaka gives food, evenings and Kansai logistics.
Give Kyoto more nights
Choose more Kyoto nights if temples, gardens, old districts and seasonal atmosphere are the main reason for Kansai.
Give Osaka more nights
Choose Osaka if food, evenings, Nara, Universal, shopping or day-trip logistics matter more.
Common split
Three Kyoto and two Osaka is a stable first-trip model. With only three Kansai nights, one base is often better than a hotel change.
Let mornings decide
Ask which days need an early start near the right area. That often matters more than hotel price.