Image comparison: Robin Wong
1) The Olympus lens is slightly wider in field of view than the Panasonic lens
2) The Olympus lens is *possibly 1/3 EV brighter than Panasonic lens (not conclusive, based on just quick observation on EXIF data)
3) There is not much difference in shallow depth of field rendering between F1.8 and F1.4 lenses (if point number 2 is true, the gap is bridged due to either the Olympus lens being 1/3 EV brighter than F1.8 or the Panasonic lens being 1/3 EV darker than F1.4. This is just my observation, not a conclusive statement)
4) Although Olympus magnification factor is 0.12x and Panasonic magnification factor is 0.11x, I find the close up shooting capability of Olympus lens to be significantly better than the Panasonic lens.
5) Panasonic lens has poorer CA control (especially shooting wide open) and corner sharpness than Olympus lens.
6) General sharpness between both lenses are almost identical
P.S.: Important to know is that Robert is sponsored by Olympus. That said we all know him for such a long time that we know that he is a very transparent and honest person. And he always tries to support his statement with fair tests and facts.