Even though this is a corner sectional and is exactly the same length in both directions from the corner, one side is going to have a seam (where the two pieces connect) and the other isn't. If you want the seam on the right, choose left facing. If you want the seam on the left, choose right facing.
Why have this option? Because some rooms allow for one of the backsides to be against a wall and the other to face the room and be visible to guests. This allows you to have a seamless presentation for your guests based on your room setup. If your corner sectional is in the middle of the room not against any walls or going against two walls in a corner it really doesn't matter which you choose.