The quality from one light bulb to another can certainly be seen by a normal homeowner. Light Bulbs are a delicate item. There are defective ones. There are generic brands. All the big brands are in the game. All in all though, there is a difference in quality. Buying the cheapest no name light bulb is not always going to be the best bet for you!
We've been getting questions lately about the lumen output and light quality of the Philips LED bulbs. Because these bulbs are rated to last 40,000 hours, there is not data for the life of the bulb yet.
A January 2011 report of 10 bulbs at 3000 hours showed that there was no lumen depreciation and no color shift at that time. So, that is very good!!! This test was based on the Luxeons Royal Blue which is part of the interior technology of the Endura LED lamps. Then at 6000 hours the luxeon LED's inside the Endura perform at 99% which far exceeds the requirements set by Energy Star!
Energy Star requirements are only 91.80 for residential and 94.1% for commercial and outdoor residential. The rate in which a LED's color is effected is dependent on how the bulb is cooled.