Here are two comparison videos with side-by-side evaluations on a number of areas, like low light, slow motion, audio, rolling shutter, and how they key.
Part 1: https://www.youtube.com/watch?v=Fe51mXb3HNY
Part 2: https://www.youtube.com/watch?v=Cw8KtH_gEn8
My opinions:
Ursa Mini: better...