Bigger isn't always better when it comes to recessed cans.
Our general contractor is giving us 6-inch-wide recessed fixtures as a standard and charging extra for 4-inch versions. If everything is migrating to LED, would we would even want a 4-inch canister? Some LEDs are quite wide and certainly would not fit in anything less than a 6-inch opening.
Six-inch-diameter apertures in the ceiling are pretty gigantic. Most architects and contractors have moved over to the 4-inch-diameter cans. Most LED fixtures come in both sizes. A fixed recessed downlight only provides a circle of light directly below the fixture; it can also create harsh shadows on people’s faces. I would have you consider using an adjustable recessed fixture, which offers a lot more flexibility in where the light can be directed. Remember, it’s not the size of the hole but the motion of the gimbal ring. Yes, the recessed LED fixtures have a higher initial cost but you get a lot of lumens for a small amount of wattage consumption; plus they last for a very long time.