Johny closes distance better while being less versatile(has less tools) than Kos in regards to striking.
Johny's got better power as well. Being a southpaw helps too.
The problem with Johny is how he closes the distance. He swings wildly and leaves himself wide open for a double.
For Johny to win this fight, he'd be best served spamming TDs, trying to utilize clinch work when possible against the cage (especially to the body), and most importantly, working on landing his Straight Left as a counter to GSP's ILK.
I'd be drilling that(^^^) over and over again if I were Hendricks. That, and work on getting off my back/creating scrambles.