A laser alignment rack improves speed and efficiency - period. All the geometry involved can be measured with lasers, string, angle finders, plumb bobs, tape measures, metal rules, dial indicators, etc. Accuracy is 100% down to the skill of the operator, whether using string or a laser. A laser alignment rack lets a less skilled and low payed technician do the work while getting good results (make it all green).
A few times I've had customers bring in a "laser race aligned" 240Z and found that the alignment was off - most often in thrust angle and caster. I've fixed it using string and other manual tools. One customer took the car back to the shop that did the "laser race alignment" and the techs said the car was perfect (thrust angle, cross camber, caster, etc.) They had told the customer that the only way to fix the car was to pull the frame.