Conrad sat in for me while I shot her from approximately two feet with:

A Paul Buff Einstein w/
– 7″ reflector
– 32″ shoot-through umbrella
– 32″ silver umbrella
– 22″ beauty dish
– 22″ beauty dish with 30 degree grid
– 22″ beauty dish with sock
– 24×36″ softbox
– 24×36″ softbox with grid

A Lumopro 120 Speedlight w/
– bare
– 32″ shoot-through umbrella
– 32″ silver umbrella
– 16″ softbox

The images were color corrected in Lightroom using the color chart on the wall.

And you know what? At least for the soft sources, they all don’t look THAT different from one another. So maybe I’m wrong. What do you think?

UPDATE:
So I’ve taken a look at them after a short night’s sleep and I wanted to point out a few things. While the light from the umbrellas and softboxes and such look pretty similar from a couple of feet away, you will notice that there is a huge difference in their spill into the rest of the scene. So if you need control over your lighting, some options are definitely better than others.

Also even though I was using strobes that ‘should’ more or less be about daylight balanced, there was a wide variation of white balance settings in post to get them in line with each other. The light from the Einstein for instance had color temp of 6000º, 5950º, 5250º, 5100º, 5500º, and 5000º depending on the modifier being used. The speedlight was even worse, 6600º, 6900º, 7500º. Remember that next time you use a strobe and think you can just set your WB to Daylight or Flash and call it a day. Nope. When in doubt, shoot a grey card at the beginning of your session so that you have a reference in post.

For me, it comes down to convenience to a large extent. If I have to carry my gear to a shoot I want to get the most bang I can get for the size/weight buck. For me lately that has been a couple of 36″ Softlighters from Photek. They fit criss-cross in my Pelican rolling case and can be used as white umbrellas, shoot-through umbrellas, and as designed with the front diffuser. Three tools in one. (Plus they’re cheap!) That said, yesterday I was shooting some corporate headshots and brought along an Alien Bee with a 46″ Softlighter and the light from that much larger source (remember, the area of a circle is π times the radius squared so it’s about 50% more area than the 36″) was lovely. Wrapped around so nice that I didn’t even need a reflector.

In the end though, soft light is soft light. How you make it and how ‘soft’ it is largely academic. If what you’ve got is an umbrella, it’ll be fine. If you’ve got a softbox, use the softbox. Stop worrying about the 5% difference in the quality of light and start worrying about making better photographs. Let me put is this way to wrap up: If you’re pictures aren’t good enough, it’s not the umbrella’s fault.

Feathered, socked, beauty dish plus a ring flash for fill. Good stuff.

Here are the results.