So which is better? "GH3" or OM-D?

No doubt the GH3 is bigger, but for me there is little practical difference -- except the GH3 has more external controls and is less cramped.  As far as weight goes, the difference (<5oz.) is negligible.  I can use the same small bag for either one, and neither one will fit in a pocket.  So....

MFT still has a major size advantage due to smaller lenses.