Thermo - fastest, with most collateral damage to skin, highest scar risk and recovery time. Best on straight hairs.
Galv - slowest, least damaging to skin, good on curliest hairs, devastating to your bank account.
Blend - Hybrid, best of both worlds if calibrated well, a balance of speed and safety. Cannot treat extremely curly hairs. Still has some risk of scarring.
Diathermy - Diathermy is so bad, it doesn't get a toggle. Don't let people diathermy you.