Some help. GH3 and OMD together. Is this silly ?

I'd second that, the two companies have a different approach to user interface. I was a long time Olympus user and went through a world of pain when I bought a G3. I've now bought an OMD and I am going through the same world of pain as I remember how Olympus do things!

Since Panasonic can give you any size combination you want and you are comfortable with the  interface, then my advice would be to stick with it unless the OMD has a unique absolute must have feature.

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Paul