Use NDF whenever you can. Some HD formats have neither. Beware of delivery specs that make no sense.
When we talk about timecode (TC) most of the times we refer to SMPTE Drop Frame (DF) or Non Drop Frame (NDF) timecode. This type of TC applies only to 30 frames per second (fps) based tape formats in NTSC. For example, a Digital Betacam can be either DF or NDF coded.
Not all HD standards run at 30fps. Probably more than half of all HD acquisition in North America is done in 23.98p which as the name says runs at 23.98fps.
For example a DF/NDF classification does not apply to an HDCAM tape shot at 23.98p. The same is true of a finished master on a D5 tape running at 23.98p. You may run into a network delivery specification asking for a DF 23.98p delivery. Such thing makes no sense. Deliver the master as you normally would.
However, some HD tapes can have DF or NDF TC. Any tape shot in 1080 59.94i standard (sometimes abbreviated as 1080i) can be coded as either DF or NDF TC.
Which should you use? For camera masters always NDF. It will make the workflow simpler and possibly cheaper. For the final master use whatever the network is asking for, most likely DF TC.
Read more about timecode for downconversions to SD.