A bit late with this but I hope it's still of use to the OP. I own both the EM1X and the EM1ii.
I'm a birder who likes to take photographs, rather than a wildlife photographer.
I switched from Nikon DSLR gear to M43 several years ago, and have never regretted it. My standard birding kit is the EM1X/300 Pro & 1.4x, easily carried on a sling strap all day and used hand-held.
Very happy with the M43 image quality: I'm not a pixel peeper (each to their own) - I require images that look fine to me on a big iMac screen and will produce good prints to A3 size when required. Those parameters are met by M43 system, no problems. IQ is similar for the EM1X and EM1ii ( though the EM1X also has handheld Hi-res ability).
Since the latest firmware upgrade, the EM1ii CAF is noticablly better than it was (not that is was bad) for stills and hugely better for video. CAF now comes at least very close to matching that of the EM1X, which is excellent.
Here are some random pics from this birder with the EM1ii (first two) and the EM1X.
To see what pro photographers can do with the M43 system, I suggest you check out the thoughts and images of Petr Bambousek and David Tipling.