m4/3 compared to Nikon P7100

You are looking at different categories of camera. The P7100 competes with higher-end fixed-lens compacts such as the X10, LX5/7, S100, XZ2, G12 etc. It works great for something that you can put in your pocket but will struggle against larger-sensor compacts like the RX100, G1x and any system where you can swap on a good bright lens rather than depend on the same compromise zoom all the time.

In addition, if you think that micro four thirds cameras lack a viewfinder then you need to visit a camera shop. You could always buy m4/3 cameras with built-in viewfinders.  Nowadays more have them than don't.