Should I trade my m43 system for Sony RX-10

You are right. I will probably keep my m43 setup. That is my conclusion based on the informative responses. At the tele end, RX10 may have a slight advantage. I am now pondering if I should get the Panasonic 100-300mm lens.

OpticsEngineer wrote:

I have had the RX10 for a few months and just got EM5+Oly 14-150 a few weeks ago (when the one week sale was running on factory refurbished cameras)

Both take very good pictures. AF speed on the EM5 is clearly faster than the RX10. The slowness of the RX10 AF is not noticeable in most situations, but it is annoying when taking pictures of the kids playing or the dog running. And as most reviews have mentioned, the electrically powered zoom on the camera is a bit annoying for being slow, but it is tolerable. RX10 is quite a bit bigger. I have read the RX10 has exceptionally good video, one of the few cameras that does not use line-skipping on the sensor. And it can be completely silent, whereas the EM5 does make some small amount of noise when the shutter is released.

So far I have not had a chance to make good comparisons of low light performance between the two. Except for some shots of city skylines at night. Spot metering seems to work better on the EM5 than the RX10. With the EM5 it is easy, but with the RX10 I have had a hard time simply using spot metering in P or A mode and avoiding overly bright lights. But with some more practice and understanding of what the camera is doing I would expect one could solve that.

If you take the sensor size and lens aperture of the 14-150 into consideration, the RX10 has a small advantage at 14 mm. At full zoom, the RX10 has a about a factor of three advantage in light gathering ability. But the 14-150 is 35 mm equivalent to 28-300. The RX10 stops at 200 mm. So the 14-150 has more reach.