The only valid way to compare lamps is MED/hr, which is related to max timer interval (Te). Yes higher % B 100W lamps are generally more effective ("hot") than low % B. But a 160W with less % B can be and often is more effective, due to more total (A+B) irradiance.
MED/hr takes in to account lamp weighted UVR erythemal "power", and is almost always inversely proportional to Te time. Standardized lamp/bed testing protocol has been recommended by TSO and others to the FDA, and someday soon more of the mystery should be removed from this whole subject.
Steve |