Actually, there are two: Materials and workmanship.

If its a cheaper product then it stands to reason that the materials are less than high quality. Sometimes that matters i.e., plastics vs metal. Sometimes it does not. In the case of electronics you have everything from the cable to the type of light and the housing they are encased in. An HID is brighter than an LED but they don't last nearly as long.

Again, if you're riding straight and level on the road all day then something like casing might not matter. However, if you do mostly off-road riding and in adverse conditions then a HIGHER quality light and casing might be more reliable and save you money over time. Just think cheap metal flashlight vs plastics that are impact resistant and are water tight.

Take for example a cell phone. I have a very cheap cell phone and it runs hot. Not only that the battery runs out in a couple of hours. Thing is, it works well enough for me since I'm not really that dependent on a cell phone use anyway.

Last but not least, there is the power cell. I have used cheap flashlights before and they start off bright but don't stay as bright for long. The case falls apart and the switches fail.

You are now a graduate of the School of Hard Knocks. Very glad you found advise here to be useful. Welcome to Bike Forums. I have a feeling you will do well in life. It's one thing to make a mistake but it takes a special kind of person that is willing to admit they did something wrong and then actually do research or take advise from others to find out that there might be a better way.

As useless as that might sound, it is the law. So the cop is compelled to bring it to your attention, and at times, enforce it.True they can "hear" it. However, the inherent problem with that is that you don't know what someone is yelling about. You then have to stop look and interpret the sound. A bell on the the hand, is instantly and universally recognized as the approach of a cyclist. Provided, it can be heard, of course. Not improve the chances? No way to be sure about that. And even a small advantage is better than none at all. Additionally there is the question of liability. If nothing else that light may significantly improve your chances of compensation should an accident occur. BTW, as a driver I always look back and warn any passengers to check behind them as well.
Good news -- maybe? Modern cars now have pedestrian detection/avoidance system built-in, so even if the driver "doesn't see you" the car will. While the industry is at it, perhaps we cyclist might get the word out to encourage car manufacturers to put these sensors on the doors as well. If we start now, within a decade getting doored will become as rare as contracting the Hansen's disease.

Its pretty much as joke everywhere. In my home state of Florida the requirement are little more than a heart beat.