I did a lot of research too when I bought mine.
I read through lots of item descriptions put on by the sellers.
When you read their description, you can't help it but to think that their item is the best.
(Come on, people pay other people to write item descriptions to convince you that theirs is the best.)
So instead of creating more headache for me, which I already have enough of, I decided to read through reviews by customers. What better place then forums, right?
I don't know about other vehicles but looking through 3 different Scion forums, it was clear that everybody liked the MobileHID kit. So I went with them and been very happy with them.
There were other kits that people were happy with but everybody seemed to praise the owner of MobileHID (Cliff) for his excellent customer service so I decided to go that way since this was my first HID conversion experience.