Manufacturing or Buying, which is better?

I was thinking of manufacturing my weapons when I reach war level 3 instead of buying them is that good?

If you see large shortages on the market for weapons or ammo you need, you can produce some yourself.
These corporations use a smaller number of workers and are very profitable.

However, you will not be able to produce everything yourself.
You will end up producing some and purchasing some.

Oh ok thanks