You know, when a PC ran at 10 mhz, upgrading to a 20 mhz CPU was a huge improvement. As the operating speeds increased, each upgrade became more incremental. Today, speed is not the issue it used to be. For what ever value it may have, the incremental improvement GH4 offers did inch out over Oly, at both DxO and Imagining Resource's evaluations. I've compared the GH4, side by side to the current Oly's. The GH4's focusing speed is noticeably faster, even in low light. As each new camera is released the improvements aren't going to be what you might consider "significant".
Another recent endorsement GH4 received was at this years NAB where it received a "Best of Show" award. A consumer camera at at Broadcast event - now that's pretty impressive. I saw the photos where Panasonic had their "varicam", a $60K camera. At times the crowds were deeper for GH4 than for the Varicam! What ever side of the fence you are on, this is a very exciting time for Micro Four-Third cameras!