GX1 + 20mm fits most coat pockets.
EM-5 + 20mm also does (tho a bit less so)
GH3 + 20mm might still fit a huge pocket but in practice will require a small bag.

add 2 more lenses that fit in the remaining pockets, and the first 2 cameras allow a small package that doesn’t need a bag, while the 3rd one doesn’t.

So there is a bit more to that size thing really.

Not relevant for your use? Could be, doesn’t mean its just as valid a consideration as yours.

Just to be clear, I wouldn’t buy the GH3 either, in part because of its size, but also because it doesn’t add anything I want to what I already have.

But that is just good, if all m4/3 cameras were desirable for me, that would just mean there is too little choice, because hey, not everyone has the same desires and needs as me. It seems much more important that there are different choices to match different needs. Makes the system grow, makes it more interesting for the likes of Tamron, Sigma etc to also produce native m4/3 lenses etc.

So nothing wrong with wanting a smaller camera, but complaining about the GH3 being too big is a bit silly I think. There are many other cameras to pick from.