For me, the advantages of self-serve machines at supermarkets are:
Neither of these is relevant to McDonalds.
How well do the machines work? How efficient/accurate?
As far as I can see, the Macca’s wall menu is completely lacking in detail. You can’t even tell how different burgers vary. And it’s hard to see what items they sell. The machines have everything categorised in sub-menus so you can browse easily. And there’s an option to customise each item, which allows you to see what the general ingredients are; you can even add and subtract them.
It’s also easy to see what is on special on the machines.
However, it can still be hard to find what you are looking for on the self-serve machines. Apparently, while some similar-seeming drinks are under the McCafe menu, others are under Drinks. I don’t think there’s a Search facility. And some flavours or options are missing.
Also missing is my “usual” order: a Keep Cup/coffee Refill, probably because the cup has to be taken to the counter with the order. I want to use my own cup and I want the 50c discount for doing so, and that can only be done at the counter. (Even then, 50% of staff don’t know that a Refill exists or where to find it on the register.)
NB. Most of this info is courtesy of my son who works at Maccas as a “Host”: the person who tries to get everyone to use the machines, serves tables, makes sure people are happy with their food etc. He isn’t impressed with the machines (due to the issues above), and while he will encourage and assist, he refuses to pressure anyone to use them.
And although he’s supposed to guide every customer to the machines, those he knows/thinks will pay with cash or have a discount card, he takes straight to the register.