One of the cons of this solution is that it non-portable, compared to the USB-sticks. Each separate signal stands out a bit more (look how easy it is to spot each separate transmitter even at low strength compared to the others). Compared to the others, small tendencies for faster sweep times, more granular data and lower noise-floor could be observed. The Cisco AP 3502 showed unexpected promising results from the test, with what seems like higher resolution and more granular data, seeing more interferers in 2.4GHz band (the three higher pitches, wireless audio?).

These may be found cheaper today, but a modest price-tag with Chanalyzer would be $600 USD. The version used in this test was found 2nd hand on ebay with a price-tag of $120 USD. Wi-Spy 2.4x can nowadays only be found as used (2nd hand market) as Metageek no longer sells this version. As the Wi-Spy 2.4x was released many years ago, the hardware has probably been adjusted and improved in the later versions (DBx-series). Wi-Spy 2.4x demonstrated a slightly higher noise-floor than the other devices included in the test. DBx with software Chanalyzer the total price-tag is $1000 USD (or ~$250 can be saved finding a 2nd hand stick.) New DBx from Metageek is $500 USD, while I found a used version years ago on ebay for $250 USD. As the Chanalyzer software detected Ekahau unit as a DBx3 it is probably rebranded hardware. The difference could be a coincidence and would need more testing to rule out. The output from Wi-Spy DBx3 and Ekahau Spectrum Analyzer ver 3 could be seen similar compared to each other, with a slightly lower noise floor using Ekahau stick on 2.4GHz.

Metageek spectrum analyzer