Which extracorporeal short wave therapy device should I choose, 27.12MHz or 13.56MHz?

Reasons for using 13.56MHz: (1) According to the International Telecommunication Association, 13.56MHz (and harmonic frequency 27.12Mhz, 40.68Mhz) 915Mhz (microwave), 2450Mhz (microwave), non-communication bands, industrial,