If you have a VR commodore, The main headlight is a H4 globe, the Highbeam light is H3.
So if you want the Phillips X-treme vision, you'll need the H4 globe and if you want to change your highbeam light you'll need H3..
H1, H4, H3 is the type of bulb, It's different sizes.
Theres many more. but H4 is normally the standard bulb in cars. It's a 2 filament bulb so it has low beam and hi beam, but the H3 is a one filament bulb so only does the job of one beam. (normally Hi-beam, or even foglights)
I dont think theres any advantages over the different type of bulbs, just different designs.
But you can't put a H3 bulb in a H4 light.
Normally your lights have a cover on them and they tell you what kind of bulb you need (h1, h2, h3, etc...)
Is that the awnser you were looking for? Aha. Theres probably more to the story than I said, but that's my understanding of bulbs.