If we're strictly talking Dmen, I'd probably slightly prefer Janik. His game is very different than Meech's, and I think for a bottom pairing his style of play is a little more useful than what Meech brings. What makes your question blurry is that its not just Meech vs. Janik for the 7th Dman, rather its Janik vs. Meech for the 7th Dman + Meech, the capable plug up front.
Good question.....tough to answer.
In the games that I saw (and personally at the Joe, like 12/31 against COL), Janik looked better defensively and more responsible on both ends of the ice. Not saying that Meech isn't, but that Janik is slightly ahead of him.