Has anyone tried using both of these lenses and is able to give me some feedback as to how they compare IQ wise?

I have the Panasonic lens which I can use on my newly acquired E-P2 body but it looks very heavy compared to the Olympus version. I also have a GH2 and realise the Olympus lens will not have any IS on the Panasonic body but I am tending to use the Olympus most of the time now due to the very compact size and the great EFV