Hmmm, wavering on Marvel Champions....that fact that it's not narrative as Arkham Horror: LCG is making me lean on the side of passing on it. Plus, another LCG is jut another money sink (thankfully spread over a long time). But on the other hand I love Marvel and actually don't own a single Marvel game (not a fan Legendary for instance, but love SOTM which is Marvel in everything but name). I imagine it's going to be super popular so FFG should keep in stock for a long while.
I think the appeal is pretty different, so that people potentially have space for both. The draw here is the characters, and playing through the scenarios with different combinations of them. It's definitely more pickup and play than Arkham.