In fancy cooking there's also a notion of a "perfect dice", meant literally to be that --- you pull the layers of the whole onion apart and cut/press them into sheets, so you have a rectangle to work with, and then dice that on a grid.
One thing you see in that video is how you're not going to get anything like that out of a food processor.
Does it matter? I can't remember cooking anything where it would have (though: I do want uniform dice for tacos).