Given roughly equivalent line waits, I've found human checkers tend to be much faster if you have more than a handful of items - they know where the barcodes are on the items so they don't have to play the game where you try to figure out which side of the soda bottle or cereal box has the barcode on it, and they already have the codes for produce memorized. Sometimes you get an incompetent or new checker, or you get stuck behind the morbidly obese lady who has to pay for $5 worth of Gatorade and cookies with an EBT card and $60 worth of cigarettes and dog food with a credit card, oh that one didn't work let's try it again, yeah it didn't work again, well now let's try this card this one will work for sure NO TIMMY I DON'T CARE IF YOU'VE GOT TO USE THE BATHROOM YOU SIT YOUR ASS DOWN AND SHUT UP OR I SWEAR TO CHRIST I WILL GIVE YOU SOMETHING TO CRY ABOUT, but just on the average I find self check-out machines to take much longer because the person doing all the work has far more experience and competence at the task in question.