100-300 lens choice: Pana or Oly?

One thing I forgot to mention when it comes to testing the 100-300. In my experience, it is impossible to get tack-sharp shots with this lens at the long end, even from a tripod with anti-shock delay enabled, in the range of shutter speeds where shutter shock is a problem. While your equipment (camera, lens, tripod) may work differently than mine, you might want to make sure to use shutter speeds outside the range between 1/20 and 1/200 to be on the safe side and very stable surroundings in every regard if you go below 1/20 rather than above 1/200. It is very instructive to turn on highest EVF/OLED magnification with this lens at the long end mounted on a tripod and see just how sensitive it is to the smallest of impacts. When testing on the wodden floor of my living room, for example, I make sure to leave the living room before exposure begins.