Photography discussions are full of desert island scenarios; "if you had to choose a single lens or if you had to choose a single light..." Well if you had to choose a single light shaping tool, you might do well to pick the white diffusion Westcott 7' White Diffusion Umbrella.
First of all it's a really big, broad light source that wraps light around your subject yielding clean highlights and rich open shadows. But due to the special shape of the umbrella there's a unique mix of soft enveloping light with the kind of crisp detail you only get from reflectors. This umbrella has a unique design structurally as well. The shaft is double walled for strength, but it tapers to 7mm to fit Elinchrom and other European flash heads. Instead of bendable metal, the 16 inner ribs are made of durable fiberglass.
This white diffusion is the softest version of the umbrella. Used in standard bounce mode, some of the light escapes through the material, slightly raising the ambient light level and lowering contrast while most of it is directed towards your subject. If you want a harder light, turn the umbrella around and aim the convex side at your subject and punch your light source through it. In both modes you can vary the light quality and output by changing the light-to-umbrella distance along the shaft.
You can also use this umbrella as a scrim over your subject to diffuse harsh light sources like the sun in situations like fashion catalog work outdoors or at the beach. Any way you use it, with the Westcott 7' Umbrella less is definitely more.