Hi Matt,
NTSC pictures contains less Movement blur than PAL because the standard shutter time in an NTSC camera is lower. Also in the NTSC-PAL conversion process are dropped 1 in 6 pictures of the original.
All this makes than the converted files will always look choppier than the original.
You can try to add some Movement Blur in post, but you will need to use a good plugin (ReelSmart MB).
rafael
http://www.nagavideo.com