What do you want to do with the lights? When I redid my family room, the goal was to light up as much of the floor as possible. For that, I used 12 6 inch, AT, IC lights. Even that didn't light up the sides and ends of the room. If you're looking just to add a little light over a chair, then 4 or 3 inch might not make much difference. It would be beneficial to determine the beam spread at the point you need light for 4/3 inch lights and see if that meets your requirements. I spaced my lights so I got as even a lighting effect I could, but you may not want that.