For my fellow gear hounds and pixelpeepers.
Unscientific yet real-world. Same umbrella, same everything.
Profoto B1 without glass dome.
Profoto B1 with glass dome.
The glass dome requires a 6/10 increase in power, but definitely spreads the light better. I found it to be less noticeable when using standard, white interior softboxes though I don't have photos. Domes used were the standard frosted glass variety.