Some of the cheap bulbs might be underwelming, you will want to stick with the more reliable brands such as sunmaster, philips, genesis etc. If there were ways to manufacture gas discharge lights cheaper, without it effecting quality and efficiency. Then the major brands would be doing it as well. They dont which is why they are the leading manufacturers.
The cheaper products have to save cost somewhere, which could be from using lower quality materials in the arc tube, electrodes, discharge chemicals etc. Which can and does effect the quality of the spectrum, efficiency and even the durability and lifespan. The efficiency differences among high quality products are usually small. But the small efficiency boost in a product can save itself on runnings costs to make up for its higher initial cost. With cheaper products the differences can be large enough to be noticable.
