We have a mix of both.
Depending on what your using your flock(s) for is what you should consider.
We sell eggs as a business. Our started pullet flock gave us the opportunity to quickly sell, then mix in with our chick raised flock(s) production.
As far as cost:
chick raised vs started pullets for us its about the same at peak production. But, started pullets life span is shorter than chick raised. Also your started pullets will never go broody so you will always have to purchase more to refresh your flock egg production. With chick raised (depending on breed) you will be able to refresh you flock internally, This will decrease your cost ratio vs production.
Our ratio:
85% chick raised
15% started pullets