Last week I've tried on display set on both Mate 20 pro and Samsung Note 9. Here's my personal experience:

I use a lot of video recording using mobile phone especially 60fps and 4K videos, but sadly Mate 20 pro quite disappointed me (cos I've been expecting improvement in video quality for Mate 20 pro). The reason is the video quality ain't good in terms of smoothness (same like my Mate 10). You can feel the video lags, especially you record in FHD 60fps and 4K. The only thing that impress me is its stabilization. Wide angle video looks good too, but still the video lags.

I really prefer Samsung Note 9 for video recording. Especially recording in 60fps on both FHD and QHD, the video really smooth. I love its 4K 60fps video a lot, but the only down side is there is only 5 min limit in this mode. No doubt Note 9 owns Mate 20 pro for video recording quality in terms of smoothness.

Mate 20 Pro:
- Good wide angle video, but it lags
- Great stabilization (you can almost throw away your gimbal)
- 4K : laggy + 10 min limit
- FHD 60fps : lags on each second (same like Mate 10)

Samsung Note 9:
- 4K 60fps : impressed by its smoothness, but 5 min recording limit
- 4K 30fps : a bit better than Mate 20 pro, 10 min recording limit
- FHD 60fps : smoothness is  awesome, but 10 min recording limit
**This is my own preference, test to decide yourself.