I try not to get into light debates anymore simply because I hate having to constantly defend my position. So I will simply say, the only experience I have had with Hella's has been poor. Most of my friends that have had Hella's have had poor experiences with them. However, they are cheaper, and I have heard that they are gradually improving their products. I haven't had any experience with them since they started making a better product. I can tell you some known issues with previous models were as mentioned before, the wiring is not the highest quality and installation is not easy. The wiring used to be between 18-20 guage, which for those of you not familiar with wiring is much too thin for a high-draw application such as driving lights. The wiring used to have poor insulation on the wire so if precautions weren't taken to prevent wires from rubbing together, the wire could be exposed and spark and cause damage. If you know what your doing, it's not HARD but it'll still take you quite a while to do. The material that Hella used to use for its lenses allowed them to break easily if they didn't have proper covers. The lenses used to fall out of the plastic housing if not properly installed. They used to use poor seals around the lenses which would allow everything from water to mud to dust to get in to the housing and into the lens. They used to use plastic housings which were known to crack. They used to have no good warranty on them, so if you buy em and they break, your S.O.L., buy another pair (but once again there cheaper so you can replace them three times before you meet the cost of a set of PIAA's). They used to use poor quality relays which were barely sufficient for the 55 watt bulbs included with the 550's, and allowed for a lot of lost power between the battery and the lights. According to hellas website they have come up with some new ones, I haven't seem them nor heard anything about them but they sound better. Check here: Dead Link Removed They used to have poorly designed posts that made them tough to aim and tighten properly without damaging the housing. The switches used to be known for burning out or burning up, and would need to be replaced, the wattage rating on the switches was set almost exactly at that of the lights. It appears that Hella also recently started releasing higher quality switches (these you have to buy extra, they don't include the better switches with the lights yet). Check here for more information on their new switches Dead Link Removed They used to use poor quality H-3 bulbs that would burn up in half the time of another standard H-3 bulb, and despite how "easy" Hella made bulb changing sound, it actually used to be quite a difficult procedure to remove the lens, change the bulb, and get the lens back in its original position without damaging either the lens, the bulb, or the housing. Like I said, these are problems that I've heard of as occuring with older designed hella lights. They may have updated/fixed many of these in there later models. Now if the debate were KC vs. PIAA, theres a lot more to debate. KC makes good lights, they have a 25-year warranty, they don't use as cheap of housings and there lenses are sturdier. They use wiring that is sufficient for the lights, the switches are higher quality switches.
I haven't seen a baja racer using hella's in quite a while but then again I'm not too into Baja racing. I did see an explorer a while back on this board that was used for Baja racing that was sponsored by Hella and running PIAA lights. I do know that those Baja Racers that I used to see would never use typically use the 550's, they would use the higher end products that Hella makes, such as the Rally 1000's and the Rally 3000's. And as I said before, I've never used the 1000's or the 3000's, I assume they are greatly improved over the 550's.
Don't say we are biased because we know good products. I've said it before and I'll say it again, I have products I like and products I don't like, and its not always manufacturer specific. For example I like warn winches but I hate the warn manual hubs (actually I hate the warn hub locking mechanism). I like certain tires and I don't like certain tires. I like certain suspension components and I don't like certain suspension components. The difference with lights is I can use exact statistics rather then personal beliefs about a specific product. Give me one person that's had problems with a PIAA light, seriously, I'd like to talk to them. So far I've never heard of anyone having a problem with one. I used to not like ARB lockers, but they recently came out with a new one which I look forward to testing so that I can once again associate ARB with a good name. I can't do this with Hella's for obvious reasons, but your welcome to try anything once