Oly 75-300 VS Pana 100-300 on a O-MD body..any experiences/suggestions/recmomendations??

I thinking of getting a long zoom for my O-MD and the only lenses I see are the Oly 75-300 OR Pana 100-300. The lens will be used mostly for birding and some far away subjects. I would appreciate your experience using the lens like build quality, sharpness at all focal lengths, handling, etc. I have seen samples of both here and I'm impressed on both? Thanks for reading.