My last geo (very happy with it) was done by a famous Lotus racer who runs a garage. He had stated not six months prior to this geo, when the car was first geo’d with him ,that he only used string, laser went wrong, all his race cars were done on string, then he bought a fancy laser thing and guess what…string is the devil’s work.
Any thoughts? (Not on his need to pay off the machine but on the principle of which to use, assuming both in accurate hands)
Great geo results can be achieved using either string or laser - all depends how competent the operative is in knowing the correct settings, & then being able to adjust the setup accordingly!
The proof is in the driving! 
My last geo was done with string, works for me. Geo my own car is on the list to Learn 
Both work well, and there are pluses and minuses both ways.
String is great, as its cheap, doesn’t need to be calibrated, is take anywhere and it doesn’t matter if you drop it. But its more challenging, fairly easy to balls up and its a bit of a pain to look at multiple settings - toe, camber, castor, etc - at the same time.
Laser kit is pretty much the opposite of all of them, live readings on a screen with red/green points to aim for, so as idiot proof as can be, before and after print outs and most manufacturers have a dedicated system that ties up with their brand of car. But, and this is the biggest but of all the ones I have used, seen or had demo’d, is they are totally reliant on a flat surface to work on, the measuring heads don’t get dropped or damaged as this throws them out as you can’t tell if someone doesn’t own up to dropping £2k of kit on the floor - and they won’t!! - and unfortunately don’t really like the workshop environment - hot/cold, the odd bit of water, being dropped, moved, wires driven over, you name it they get all the abuse you can imagine and have a sulk at the most inopportune moments.
Most important bit is who is on the other end of the ruler/laser and what the numbers are aiming for.
Thanks Prof.
my local place tried to Geo my BM, and because of the way their workshop is built one side is open to the elements and the wind blew the rig around so much they gave up.