I think they all have a purpose and what you want to do with them, or how you want them to look makes a big difference in what you choose. You can get certain sizes and finishes on only certain models so you have to decide what you style, size, etc. you want. They are almost all the same but different.
The KC's, I had a set on a truck, did they work fine, yes. However would I buy them again, probably not. They sucked a lot of juice and I know there are better alternatives out there.
When you look at PIAA or Hella, I think they do a lot of research on how to get the most light output with the smallest wattage vs KC just throwing in a super powerful bulb in the case.
If I were in the market I would be looking into Lightforce, Hella and then PIAA. In that order. Lightforce has the super cool option of putting covers on their lights for certain conditions.
Warn also has a set of lights that can be switched from spot to like a flood with the flip of a switch. I thought that was a super cool option if you only wanted to mount 2 lights. I haven't seen them in person or any reviews but they had just come out at the time I was buying my KC's.