Lots of photographers and cinematographers are thinking about sensor size today with so many affordable full frame options and high priced crop sensor cameras available. Manny Ortiz made a pretty good a7rII vs a6500 real-world comparison video, while biscuitsalive compared the Sony a7S and Panasonic GH4. Sensor size largely comes down to preference today even when shooting high ISO until a point, but some can see a difference that they find tangible. I personally prefer larger sensors but acknowledge there is little difference between APS-C and Full Frame today, but I doubt m43 will ever fully catch up.
Sony a7rII B&H Photo / Amazon / Adorama
Panasonic GH4: B&H Photo / Amazon / Adorama
Sony a7SII: B&H Photo / Amazon / Adorama