Both approaches work, and there is no single answer. The choice is based on the available terrain, the rental equipment available, and other specific considerations. Most ski schools end up teaching a wedge-based progression, as this seems to work for most people, especially in group lessons settings. There are specific cases, however where a straight-to-parallel approach might work better, depending on body shape or sports background. For example many young hockey players or rollers skaters do well with straight-to-parallel.
