Efficiency and Power Factor
The two junior models have the same efficiency. They are less than 80% efficient, which is very poor for modern products. On the other hand, that’s just a trifle considering the other drawbacks of these PSUs such as a scanty selection of connectors, tangled cables and noisy fans. The power factor is no good, either, not reaching even 0.95, but this parameter is unimportant for the absolute majority of users.
The senior model is somewhat better in terms of both efficiency and power factor. It is far from breaking any records, but notches 80% at least.
The biggest problem with the bundled power supplies from Chieftec is that they are no match for the system cases they are installed in. These entry-level power supplies would be appropriate for inexpensive cases (including microATX cases) that might be used for office computers. But I don’t think it is right that a huge system case capable of accommodating a dozen HDDs comes with a power supply that offers only four SATA connectors. A handful of adapters won’t make the system case more reliable or easier to assemble. Therefore, I guess you will want a different power supply if you like Chieftec’s system cases. Or you will want a smaller case if these PSUs suit your PC configuration.
There is no point in distinguishing these PSUs by their wattage ratings because my tests show that they have nearly the same effective load capacity. The GPS-500AB-A has two advantages over the 400W and 450W models, though. It is quieter and offers a selection of cables that is sufficient for assembling a modern PC configuration without adapters. Alas, the GPS-500AB-A only comes in huge Big Tower cases as yet.
Summing it up, I would prefer to see Chieftec cases without any PSUs than with PSUs that match their format and purpose so badly.