IR is reputed to deeply penetrate tissue, and may be better for that reason at relaxing the aches and pains from spending a day on the mountain. And you're right, the air in IR saunas doesn't get overly hot, it is the action of the far-red radiation that warms surfaces.
You can't steam in an IR sauna though. So there is a drawback. Oh, and don't take a glass of water or any other objects into an IR sauna, the glass will get extremely hot from absorbing IR radiation. Trust me, I speak from experience
