Hello. I actually bid in ebay for a HID kit, the seller is asking me which harness would I prefer. If the one that hook up the power from factory plug or the one that hook up the power from the battery?

I have never install a HID so I have no idea, which one you recommend me? which one would you pick?

I have a 525i BMW 2002

I would thank any help, I have only a little knowledge of HID.