LST and Scrog let you light the plant more evenly, and allow you to expose more bud sites and allow them to develop. I use them to get the light to the interior so that the buds that would have been little popcorn and fluff have the chance to become monsters. It does affect the height, but at least on mine, nearly every bud thinks it is a top. I have also heard that lighting more evenly creates a situation where the buds are all equally potent, rather than having more THC in the buds that got more light, or became more dominant. I cannot confirm that theory, as I have always scrogged, but it has always seemed reasonable to me.