Sorry to hear that you had such difficulties with the X-T1 & the 56/1.2 combo!While I'm inclined to agree with you and my next camera purchase will probably be an E-M1, from what I think I know, the GH4 has some advantages in the flexibility of its AF system that I can see being very useful for an action shooter, and I cant help but always be impressed at how panasonic managed to improve performance so drastically, to arguably the best among mirrorless cameras, while only using CDAF. I shot a wedding today, side by side with an X-T1 and my E-M5 (not really action, but there was a lot of dancing =P), and being able to use the touch screen to set my AF point while looking through the EVF and set custom AF points were both incredibly useful. The former was kind of like manual focus tracking. That said, Olympus' face detection is still the very best out there. Panny's is still good, though.
The X-T1 plus 56mm F1.2 was a bit of a frustrating experience with false positives and slow focus. I ended up reverting to manual focus or just using the 45mm f1.8 on the GH4 or E-M5 most of the time. Shame, because the 56mm is a beautiful lens.
But, I'm kinda shocked that you would even attempt to shoot a wedding with the X-T1 if you were already having (knowing) these difficulties going in? (Referring to the GH4 review thread that you wrote and the poor X-T1 tracking you mentioned)
Testing out a camera is one thing, missing a client's "most" important moments are another thing..