I haven't seen any real reason that lumateks are considered good. I suspect that at this stage of the game that they are considered the best because they occupy the highest price point.
In this market there doesn't seem to be any kind of independent product testing and limited sharing of information. My local hydro store (a lumatek dealer) had stated that none of the brands they sell had distinguished themselves as being signifigantly more reliable than the others. They are all made in china.
I know that measuring real ouput from a ballast and bulb requires an integrating sphere which is a pricey bit of equipment and it would be a huge mistake to assume that ballasts from the same company are the same week to week . Operating environment, power quality and even circuit quality can effect a ballasts operation which makes it even more difficult to compare apples with apples.
It would be great to get what you pay for but with the dynamics of a global market that just isn't the case at all anymore. I think that you are more likely to get the best marketing department when buying at the highest price point.
I contend that there are great ballasts at all price points and that throwing money at the problem is the wrong way to go about it. I bought 2 Via Volts that may turn out to be shit. I'd heard that I could get lumateks for just 40 dollars more and at first regretted my purchase until I saw that my Via Volt ballasts actually have BETTER specs than the lumateks I was again pleased with my purchase. I do think that it would have been a good decision to buy the lumatek at that price point though. I would have kicked myself and seriously regretted my purchase if I'd bought a lumatek ballast for what some companies are charging for them.
I don't believe I would regret my purchase even if the Via Volt ballasts fail during my first grow. I haven't seen anything anywhere to lead me to believe that any of the ballasts made by any company are unreliable and that , unfortunately , failures happen.