Over the period of eleven years, I tested dozens of models, and literally hundreds of devices, both Bluetooth and Wi-Fi. This was with my own companies products and those of our competitors, and others.
I also tested PHY level parameters on these products, with precision Wi-Fi and BT test gear, but that is a different story.
One thing I learned is that you cannot trust most manufacturers when it comes to their range or PHY claims. Things have gotten better over the years, but most range testing is poorly done. Marketing types often get their claws into product claims, much to the chagrin of a company's technical staff. Product managers, whose pay is based on device performance, are some of the worst culprits.
To truly test range, a test AP must be located at least 8 feet off the ground, and have a clear path unobstructed in the Fresnel Zone. Each device should be tested in at least four orientations, starting out at the MAXIMUM expected range first, NOT the shortest. Many devices will connect at a short range and then move away successfully, but only better products will connect consistently at the longer range. To perform this test correctly, the AP and clients MAC tables must be cleared between trials.
Some devices come in different color schemes, which may be controlled by the doping of its plastic body using different coloring agents. From a range perspective, the worst dopants are metals or Carbon. Thin plastic wraps can also cause problems if they have the wrong materials in them.
Clients also need to be tested in both frequency bands, as dopants might only have a severe effect in the 5 GHz bands. Multiple channels in each band must also be tested. Modern dual band antennas are intentionally biased towards the 5 GHz band, to counteract transmission losses, but there is usually never enough gain in a small device's antenna.
If you read the actual specs for some Wi-Fi antennas, you will find that they actually have losses rather than gains at some frequencies or physical attitudes.
I would be interested to hear your experiences with your client devices.