- Faster frame rates tend to be more clear, slower more softer like film.
- Converting interlace to progressive works, but never convert from progressive to interlace.
- Shoot in the frame rate and frame size you are delivering with.
+ If you're delivering for the web, computer screens, or projection systems, shoot/edit/export as progressive.
+ If you're delivering for television broadcast, check with the station for their specs, which will probably be interlaced.
Possible occasional exceptions:
- If you want slow motion shots, shoot with 50p, place in a 25p timeline, use the "Conform" command.
- If you are shooting fast motion such as action or sports shots, and want them clear (less motion blur), shoot a faster frame rate, interlaced, with a fast shutter speed. Otherwise always shoot/edit progressive.
It all depends on what format your timeline will be in for editing, and what format your export needs to be.