blades

Hi, I have a A180 2006 which seems to have dodgy front window wipers. (fuses checked all ok) I've done a bit of internet research and it seems that proper attachment of the wiper arm to the spline stub if critical, and they do look a bit wonky when in the "rest/off" position. (see attached...

I bought some new wiper blades from the MB dealer (£30!!) They are curved unlike the earlier ones which were straight and don't have a spoiler. My car takes the older style blades with a frame unlike the later slim version. Which way should the curve be? Should the driver's side blade curve...