There is not much difference in a health benefit. Both achieve the heat shock protein activation, lowering inflamation and inrease endothelial function.

Traditional heat the air in the sauna and hence raise your temperature.

Infra red heat you directly with a less effect to the ambient temperature.

Infra red typically does not go as high as a tradtional sauna in heat.

Ive used both.

The infra red are good on a warm to hot climate.

A cold to cool climate the tradtional feel better imho.