Infrared and traditional saunas both raise your body temperature, but they get there in different ways, and that difference matters more for your buying decision than most marketing pages let on.
Traditional saunas heat the air around you, typically to 150-195F, with the option to add steam (loyly) by pouring water over heated rocks. Infrared saunas heat your body directly with light panels, which lets the cabin air stay cooler (100-140F) while your body still reaches a comparable internal temperature.
If you want the classic steam-room feel and don't mind a hotter cabin, traditional wins. If you want a gentler air temperature, faster heat-up, and don't need the steam element, infrared is usually the better fit — and it's also the more common choice for smaller indoor spaces.