Your points are valid, but your estimation of Korczak is a bit low. Korczak is actually a very good outlet passer with unheralded offensive tools. Korczak's offensive abilities are more impressive than Johnson's defensive proclivities, to this point. Am I saying that Korczak is better? No. But the upsides of the two players need to be examined.
Johnson's obvious attribute is that his skating ability is absolutely elite. His entire offensive tool box, though raw in places, is impressive, to say the least. Defensively, however it's a bit different. Though his smarts and speed make him a defensively sound player, he can be beat in one-on-one battles and absolutely does not like to play physically. He's 6'0, but very lanky and not very physically strong. Though this can be improved, it is a prudent projection that he will never be a guy to clear creases or be a physical detriment to opposing forwards. So we're talking about a guy with bout 50+point upside offensively that can become an above-average, though not shut-down, defensive player.
Korczak certainly trails Johnson in the skating category -- though he is an above-average, mobile skater, he is nowhere near Johnson's elite skating. But in every other offensive category, he is right there with Johnson -- his shot is better, his passing is just as good, his puck handling is just a shade below. Defensively, Korczak has elite, shut-down potential. At 6'3-200 he's incredibly strong and physical, routinely clearing creases, winning corner battles, intimidating opposition forwards. If he can improve his positioning and gap control a bit, he can become a true shut-down beast in the NHL. So we're talking about a defensive, physical monster with 30-40 point upside.
My personal feeling is that I'd rather have a player of Korczak's upside than a player of Johnson's upside, though they are both certainly desirable assets. Add into this the fact that Korczak plays RD (the Devils biggest organizational area of need) and Johnson LD (Devils stronger there with Smith and Davies on the way). Add into this the fact that Johnson's style is similar to Butcher and Davies and the Devils have no one in the organization remotely akin to Korczak (and they desperately need them). With those factors in play, to me Korczak is an obvious and clear choice over Johnson.
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