Many experts say that MMA is safer than boxing. In MMA, once you've stopped intelligently defending yourself, the fight is over, you get a medical suspension for 3 or so months to recover and come back better (hopefully). Boxing has the 10 count once someone is rocked. So they have an opportunity to get back to their feet, likely still semi conscious, letting their opponent tee off on them again, and as many times as they can stumble to their feet.
Many times in MMA the fighter is knocked out, hits the ground and comes too a few seconds later. In MMA the fight is over even if the fighter thinks they can continue. In boxing it wouldn't be.