Is there a Magic Wavelength?

No. Some manufacturers say one wavelength is the "magic" wavelength and other wavelengths, in the therapeutic window, are less effective for healing. If you study specifications for laser diodes, you will typically see that lower cost "810nm" diode can range from 800nm to 860nm when tested. For an additional cost, a diode manufacturer will pick and choose diodes from a larger run if you need a tight-tolerance higher-cost diode but most manufacturer do not do this. They purchase standard tolerance diodes so your 830nm laser could be actually operating at 800nm. If you check the specs on a 660 nm laser diodes like the ones used in medical lasers, you will find that the manufacturer specs the range from 635 nm to 670 nm. That means that a 660 nm laser might be 635 nm and vice versa.

Don't be fooled by anyone who says that 660 nm is better than 635 nm or that 830nm is better than 810nm or any laser claiming they have a superior wavelength within the tolerance of a standard laser diode. They are probably the exact same diode but the manufacturer is over-marketing a non-existent difference.

The actual output wavelenght is also based on the temperature of the diode. The output change for a typial IR diode is 0.3nm/oC so the wavelenght when you first turn a system on (20oC) will be 3 to 10 nanometers less than it would be at the full operating diode temperature (up to 40oC). This also shows that any manufacturer that is saying their system has a superior specific wavelength is probably over-marketing.

Emphasis on the higher frequency ranges (IR) and deeper penetrations are echoed by a majority of cold laser manufacturers. Although each manufacturer insists that their wavelength is optimal, there is no general consensus on the sweet spot. For some conditions the lower wavelength is best and sometimes a higher wavelength is best therefore, having a system that is capable of dual wavelengths gives you the most flexibility.