I was playing with modifiers the other night just to see what lighting they would give me. This particular time, I had a McGillicuddy 36" multi-modifier configured as a vertical stripbox as my main/key light and a gridded flashgun as the hairlight.
This is the result of having the stripbox to one side at same height as the head and tilted down a tiny bit:
Contrast the above to the following image where a reflector umbrella was used (feathered heavily around) to light the face with no second light to highlight the hair:
Things to note are the shape of the catchlights in the eyes and the way the light falls off.
I wouldn't be without the McGillicuddy modifier (I have 2 of them) now, but it's by no means the only one I own or use.
The conclusion is that no matter how portable/light/convenient a particular modifier is, if it isn't the right one to give you an effect for a particular image, it doesn't matter how portable or light or convenient it is.