Growlampe

You can answer these questions simply by looking at the light frame. QBs are more centralized and tightly packed diodes, so they don't distribute light as well as the bar/strip type frames. how many plants it is good for entirely depends on how large you grow your plants. Efficacy is the primary determinging factor of quality. Efficacy impacts how many watts you need per sq ft to do the job right. It effects longevity. It effects how much heat is created, too. Unfortunately most light producers lie about this stuff. It's easy to double-check by using information from samsung.com or the original manufacturer of the diodes if a different brand. The lm301 is common and will be used in the example. LM301 is tested at .2w per diode. Any deviation above that will reduce efficacy and longevity while increasing the heat produced (indirectly proportional to efficacy). You may get 3-5 years out of a cheap to mediocre light, but you'll get 7-10 from a high efficacy light. so, if it's a samsung lm301 based led light, simply divide watts by total number of diodes for a rough estimate of watts per diode. If significantly higher than .2w/diode, you'll never reach 50,000 hours of use, you'll use more electricity to get the same yield and it'll generate more heat while doing it. Longevity drops fast as you run the diodes with more wattage. The low-end lights will be about .5watts per diode. High end lights will be .20-.25watts/diode. If they won't give that information, don't give them a fucking dime.

The choice of lamp depends on the size of your growing area and the plants you want to raise. After that, I would ask myself how many watts the lamp should consume and how much you want to spend, and based on that, look for the best model with the best lighting, LED chips, light spectrum, etc.