Hello,
I'm somewhat new here... Been lurking for a little while, and finally purchased a ti a few days ago.
Anyway, my intention is ONLY to give you my thoughts. I don't want to start any waves or try to sabotage this group buy, as I know they take a lot of legwork for the coordinator to setup. I do give a big thumbs up to the coordinator for taking the time to research and communicate to the vendor. Something that easily gets overlooked on the internet.
I just want to offer my thoughts and personal experience... Anyway, I chose to pay a little bit more for the HID setup because I have read about premature failures and malfunctions (both inside and outside a year). Rest assured, I am not affiliated with any aftermarket car manufacturing company or anything of the sort -- I'm just a fellow bimmer enthusiast.
One thing you might want to find out from the vendor is the cost of replacement parts (outside of their warranty period). And then judge cost of ownership from that perspective.
I chose to go with a company called Xtec. I know that Xtec offers a LIFETIME warranty on parts... They tend to cost a little more "up front," but in the long run could work out to be cheaper in the sense that you don't have to pay more for replacement parts. I purchased an HID set for my m3 a couple years ago, and had a ballast go out on me after about 1.5 years of ownership... I called the manufacturer, and normally would have costed $130 for one side. I only know this because that was the deposit they charged on my credit card for the return item, which was credited back to me when they received the faulty part. And get this -- they covered postage for the part -- both ways!