matt i just find them easier to use on velux,windows above connies,any awkward windows,deep ledge windows etc.
plus cos the brush is screwed directly onto the gooseneck it stops the annoying brush movement that you get sometimes with screw on brushes.
i changed the extreme brush for my sill brush and IMO its awesome for most domestic work!
im well pleased with my gooseneck.its very strong and ultralight.