I don't have an EM1 but I do have an EM10. Comparing the shutter and EVF black out when shooting both the EM5ii and EM10 at 1/30, the EM10 has a VERY much longer black out in EVF when shooting while the EM5ii is very short. The silent electronic shutter is also super nice, silent and no shock feeling. In all the EM1, 5 and 10 you can feel the shutter shock in the camera when it fires. But I feel the EM5ii mechanical shutter is very well damped and quiet compared to EM1 and EM10.
Looking through the EVF of the EM5ii is obviously a hella nicer than looking at the much smaller EM10 EVF.
So while I expect the image quality to be pretty much the same, I think the shooting experience in the EM5ii will be much nicer than the EM10. Anyway, I'll be bringing both for a photo shoot tomorrow at Esplanade Park.