Composite video is not 'dead' but you're only going to find it on small security/lipstick cameras and maybe some low-end consumer 'toy' cameras and you'll still want either a professional
monitor or a
CRT (ideally a professional
CRT) to display as real-time as possible. It's definitely harder to find what you need for a real-time composite feed than it used to.
SDI (and HDSDI and 3GSDI and ...) is true realtime and the signaling format is backwards compatible*. If you get a professional (3G/HD)
SDI camera and feed it into a professional (3G/HD)
SDI display then the only delay you should have is the capture and display time delay - there shouldn't be any buffers in the way and the
image is 'scanned' down the cable just as it was for a
CRT with a flyback. Note that a CCD capture device does not scan sequentially so there may be some added minor delay here so you would probably want a CMOS imager and most LCDs display what is essentially whole-image at once so you may have some minor delay here but those delays even if you have them should add up to at most 2 frames (1/15 of a second) - the better you configure your
system, the lower that delay. If you want to talk standards and details (SAV/EAV/color encoding/
etc.), let me know.
Oh, and I don't feel like I'm old enough to be an "old timer" but I can wax philosophically about
NTSC, NTSC-II, NTSC-III,
System B/G/I/K/...,
PAL, SECAM, et al. all day long.
* seriously, us TV folks keep making sure everything works in lock-step with the previous generation so in theory you could take a 12GSDI dual link 4K signal and generate a
NTSC black and white [not NTSC-II or NTSC-III color] signal in realtime and the most delay would be less than a front porch, likely less than a color subcarrier wave or two - if someone has made the hardware to do this is a different question.