It’s really hard to say. In business, you want to delight your customer, make him feel he is getting his money’s worth, that a job is done right. Especially true of electricians. OTOH, you cannot give away the store, do a lot more than is required.
When I wired my own house, I used bigger boxes than was necessary, partly because they were easier to wire, partly because they are easier to rework, if you want to add a circuit or change out an appliance or switch. Contractor wiring is generally (though not always) done “right”, but electrical contractors especially, always seem to do things as cheaply as possible and still comply with code. But you don’t pick them, the general contractor does.
When one wires their house, using larger boxes and heavier wire is a safety and code issue. The number of leads and romex gage determine the minimum square inches the box must be. If one wants to spend a few extra $ to do that it is a personal choice. I do it. But when working for industry the original "rule" still applies: enough to get the job done correctly.