Oops, I see you have edited your post so I guess you have found out on your own, cindy.
If you want the softest brushes, you should definately get blue squirrel brushes. I own the B505BkSl (blue squirrel & sokoho goat) and it is, beside the Chanel Les Beiges kabuki (synthetic), the softest brush in my collection. And I have swapped away most of my MAC face brushes (except 165) a long time ago because they are so scratchy.
Blue squirrel brushes do however give a rather sheer finish. Mixes with goat or horse hair are said to deposit more pigment, but still give a very soft look. I am very pale with transparent skin and find that these kind of brushes can give me a very diffused finish that other hair types can't. Just thought I should mention that, as darker skin tones that need more pigment as far as I know, so depending on the product used more layers would be needed.
Scroll down to the comparison post to see what I mean with very diffused, even compared to Yachiyo type brushes:
http://glossedintranslation.com/2011/12/07/comparison-hakuhodo-blush-brushes/