Level 4" smooth finish on the drywall.
We prefer the look of a smooth finish, but it requires more skill and work to get good results. It will show minor irregularities more than a textured surface. So it is important to get the wall installed flat, and the joints sanded very smooth and level.
Going the extra mile, our drywall contractor sprayed on a sandable topcoat to really even things out, giving us an almost "Level 5" finish.
I am a mix of emotions: thrilled for the better quality walls, and nervous as heck to turn this guy loose in the house with a spray gun.