CB, I think snaplines can fill in when edges get waney, so it can be faster to layout your timber. Also snaplines are more fun to layout with than edges, IMO.
Alp, the only trick about snaplines is you still need to create a flat face for your sheathing/flooring, so the lines should always be set out in relation to the timber faces. Use a level or plumb line to get the timber ends in line, placing twist and bow where they work best.
