I'm coming from the HID world, so take this for what it's worth. These are the factors that most affect stretch in my experience:
1. Genetics - single biggest determiner. If you don't have head room, don't grow lanky, 12-week sativas. nuff said
2. Light intensity - doesn't matter what light you use, if lighting is inadequate, plants will stretch towards them in both veg and early flower.
3. Heat - the hotter it is, the more they will stretch in early flower as a stress response.
4. Spectrum - it's well known that far red induces stretch and that blue keeps internodes tighter. I've flowered under MH and HPS and the results speak for themselves - less stretch and more compact nodes under MH (blue/green) comparing watt-for-watt to HPS (red/yellow). However, you still need that light intensity.
The kicker is that HPS always outproduced MH in flower due to two factors: HPS is more efficient than MH (more light per watt), and has more red spectrum. Full spectrum CMH reportedly has the best of both worlds, but I've not tested it again HPS. I like that CMH has a bit of UVA/B in it, but don't buy the 315wCMH > 600w HPS hype.
I suspect redder LED spectrums will always outperform bluer spectrums, and having spoken to a few people, that seems to be the case. So I've just bought some 5000K strips to play with in veg, but when I move on to flowering, I'll be looking at something in the 2700K range to emulate my old MH veg/HPS flower set-up.