When self checkout desks were setup in my grocery store, there were 2 cashiers and 3 self service points. The queues to cashiers are different, but there is a single queue to self service. After a few observations I found that longer queue to selfservice usually goes faster. Probably because of two reasons:

1. There is one more cashdesk in there 2. The payments are done by card, whereas there those who pays in cash to the cashiers

In general cashier, of course, faster than a customer in operating goods. But there are other slow processes involved. Like: loading goods on the tape (not present in selfservice), paying with cash (some advanced selfservice desks have that though), packing goods into bag (could be done right after scanning in selfservice)

P.s: the location of a barcode on a box almost does not matter with a good scanners doing scans in two dimensions

I've noticed the self-checkouts seem to have some safeties in place which the normal cashiered checkouts don't (because they assume the cashier is trained). For example, if I buy ten cans of the same soup, the cashier's system seems to let her scan one can ten times, whereas I can't do the same on the self-checkout, even the Walmart ones that don't care about the weight being placed. They have a "prevent double-scan" delay built in that is long enough I may as well grab the next can.

bananas is 4011 almost everywhere. an experienced cashier has the code for ginger root memorized.