First they might not fit.
Second, and the main reason is how LEDs are. They aren't like halogen or HID bulbs that spread light everywhere. LEDs use chipsets that have specific individual beam patterns. To spread light evenly from an LED bulb you need a projector style housing, or parabolic type housing at least so it can spread the light towards the direction you want. LEDs in your factory housing will throw most of the light where you don't need it or want it. They will overpower, and work slightly better, but you will also blind people and have odd cut offs if you can notice em.
The cheap improvement is to use a brighter halogen bulb, and do the 4 hi mod, so your brights come on when you need em. The mod makes it so your lows stay on, instead of switching between the two.