Class IV lasers such as K-laser, Avicenna, LiteCure, Pegasus extol the virtues of high power. At the other end of the power scale are very low output devices such as scalar wave and Erchonia that claim some magic in frequencies with abilities to treat through clothing (not possible in case you were wondering).
Peter Jenkins wrote an entertaining rant on this topic.
It’s an old article now so only on Wayback Machine but well worth a read Click here