The camera here is a Samsung HMX-Q10P (P likely stands for PAL: the N model would have 60fps instead).
The videos I upload usually are 25fps either way, but strictly speaking 1080/50i will never give me the odd lines when dropping every second frame, so I rely on the deinterlacing algorithm of my video editor (Shotcut in this case which may use ffmpeg or other stuff internally) to deliver reasonable content.
I've made a few attempts at fast moves of the camera shooting 1080/50i and I have not been able to see noticeable staircasing when creating 25fps output from that by reexporting from the video editor. However, I am not sure how much quality deterioration the interpolation of the odd scanlines will cause.
So assuming the desire for best results, would I be better off shooting in 1080/50i or in 720/50p for videos without global movement (fixed mount, no zoom while shooting) and moderate local movement (close-captured single musician), and how would those considerations change given different material?