24p (if you can remove the pulldown before editing) or 30p. Interlaced video complicates matters. Also, you'll want to use a fast shutter to minimize blur.
With a PAL camera I always shoot Chroma Keys in 25p. Try to keep movement of the talent down to a mininmum (for shadow purposes as well as strobing) and light the background well and you will get a good key in 24p or 30p mode. The DV format is not ideal for full screen keys as it can be a bit obvious. However for web or podcast sizes of 320x240 or 480x360 the DVX works very well.
thanks for the suggestions. I have not shot 24a yet, so this will be a good test. Fortunately this will be for web use. I bought dvGarage's keying software which seems to do a good job.
