I'm no great shakes of a cook, and a mandolin suits me just fine.
Let's face it, if I haven't developed finely tuned knife skills after
53 years of cooking, I ain't gonna.

A chef once told me the fine chops or slices expose more flavor from
the dicee (?) So that's a nice goal.

Advantage over a food processor? Only one item dirty which goes into
the dishwasher. Slices instead of bits, but if you turn your back on
that food processor, it's mush. Slices look better in finished
product. They'll never know how they got there Knife or magic
machine.

I take the whole bunch of celery, rinsed, grab it with both hands,
hold the mandolin steady with my gut and whale away at it. About 4
swipes - done.

My present mandolin is a $5. cheapie from a deep discount store.

Joan