I haven't found a definitive answer to this.

Are the headlight assembly the same in terms of low beam cut off/reflective area for both the halogen and HID option?

If so, are the difference just the bulb socket and auto-leveling system?

 

The hologen reflectors are different from the hid reflectors, the setups is a totally different type. You have the ballast built into the headlight assembly along with the auto leveling system. The best option is if your looking to get better visibility out of your rx is to just get a headlight projector retrofit, I have one on my rx and let me tell you, so much more better than the old hid reflector setup, it also blows the basic hologen setup out of the water!

 

Anthony,
What exactly did you get & where? Do you remember the part number? I'm not finding anything that matches a "headlight projector retrofit".

 

Hey there again, unfortunately they don't sell the RX300 headlight with the projector installed, I built my set LOL! They have been on the Rx for about 4 years and the oem headlights were already fading, I'm going to buy a new set of lights and retrofit them so I can have a new updated setup haha!