For coding OLED is my favorite because in my OPINION it reduces eyestrain. In my experience the two biggest factors in eyestrain are: too small of a font for your eyesight, and too bright of a screen.
With a normal LED-IPS display you can turn down the brightness to approx 25-35%, but even then the screen remains pretty bright and below that the colors and contrast seem to wash out slightly.
With OLED because each pixel is lit as opposed to the entire display, working in a night mode means you're really looking at a very lightly lit screen even on a full page of white colored code.
Plus the white code really pops out because the background is much much darker than other technologies. On other display types the software asks for black but really gets a shade of grey, this is due to unavoidable light leaking. On an OLED it asks for black and gets actual black.
That all being said, OLED is great for coding, IPS might be better for color reproduction (e.g. photo editing) and wide angle viewing, and neither IPS or OLED is great for gaming currently (due to poor response times, etc).
PS - Obviously this post is only about display technology. In the real world other factors may come into play like relative price, resolution, orientation rotation, reliability, and so on.