Back in the 4/3 days, Olympus had the distinction of a few large cameras with comparatively small sensors. The E-3 for example was roughly the size and weight of a Canon 5D, despite having a sensor 1/4 the size. You could argue that the lens options made things less comparable, but it made the argument for high-end 4/3 hard (particularly that body and the SHG lenses). Having finally managed to get my hands (briefly) on a Sony A7r, I wonder if we're headed down the same path again. Don't get me wrong, there are some truly tiny m4/3 bodies and lenses that I don't think anything full-frame can compete with. But for a camera with high-quality zoom lenses that will be used heavily, there's a size beyond which downsizing starts harming ergonomics and force major compromises on lens quality. I guess everybody has their own threshold, but mine is the E-M1/E-M5. Nothing smaller really handles well with the 12-40/2.8, let alone the 50-200/2.8-3.5. Of course, the Sony full-frame mirrorless are basically the same size as the E-M1. Granted, the system is nowhere near as mature as m4/3 and at least for now there's a significant cost difference, but with some effort, one can put together a system that aside from longer telephotos is pretty competitive on size and quality. As time goes on, I expect the difference in cost will drop too. In short, I wonder if we're repeating the trajectory of high-end 4/3 with m4/3 - insufficient differentiation (size, weight) given the significant disadvantage of the smaller sensor size. Thoughts?