Flash Burst Profiles
While looking at power ratings numbers directly can be useful, another practical approach is to look at the total area each flash could cover at any zoom setting. That is, consider the flash to be fixed in one place and examine the possible places a single subject could stand and be appropriately lit. This takes into account both flash reflector zoom angles and the raw power needed to reach into the distance.
The following flash burst profile images use the actual correct angles for zoom settings. The shape and proportion of the profile remains the same regardless of aperture and ISO, but of course becomes smaller. And obviously light doesn't really work like this: the hard-edged cutoffs are a fiction — but a convenient one.
