I have seen variations in the reported efficiency of LED light bulbs and it does not seem to correlate with price. I'm wondering if there is any trade off between the things done to improve efficiency and life span of these products.
There is a clear impact on longevity from higher temperatures. Things that help cool the light bulb cost money. But I can't think of how this would correlate with efficiency, other than a cooler LED working at a lower voltage, so more efficient.
What would negatively impact the efficiency, or the life span, that would trade off between the two?
To put it in a nutshell: if, for a given light output, a light bulb is constructed with more LED elements, each running at a lower current, then the bulb will tend to be more efficient and last longer, but will be more expensive to manufacture. Typically the higher cost will be passed on to the consumer, so on average, you can expect cheaper bulbs either to fail faster, or to have lower light output, or both. I found a dollar store bulb to have lower light output than a premium bulb, for the same claimed lumens.
Having tested a few bulbs with the same claimed lumens, I have concluded that the number is not the actual measured light output, but is rather a "marketing claim", and in general, cheaper bulbs produce less light than more expensive bulbs for the same claimed lumens and power consumption.
I have also found that the claimed power consumption (e.g. 8 W) is usually pretty accurate.
So if you want the best lumens/watt from a bulb, then I would go for the more expensive ones. I have been finding that Philips bulbs perform better than most in my tests.
The other important factor is dimmability. In the USA, dimmable bulbs cost far more than non-dimmable bulbs, presumably because of the more complex circuitry. I have found bulk buys on non-dimmable bulbs at a few cents per bulb (but I had no idea what to do with a carton of 24 bulbs for $9.99 when I only needed six).