How to convert 25p to ntsc dvd?
I personally would use media encoder and let it do the conversion. Convert it to a mpeg2-dvd format and pick a preset, you can adjust the preset to your liking. ME would do most of the heavy lifting. At this point I trust them to do the best job.

I find that nothing beats actually trying it though, you're not really out anything but time. And very little time at that. It's not like your encoding each frame by hand. :)

Alex