At this point, I would take Oduya for half the price.
If we had Campbell, we would have to let Stalberg and Bickell go this summer, and trade someone to make room for Kruger and Leddy. Without him and his contract, we can probably keep Kruger and Leddy without making any moves, and keep one of Stalberg/Bickell unless they unload Olesz and/or Montador and in that case we can keep both.
We have a good situation leading up to 2015-2016, where Toews' and Kane's contracts expire and we only have 4 players under contract that will take up nearly 35% of the cap space. That would have been Campbell's final year under contract, which would have bumped it up to 5 players and 45% of the cap space taken (just quick estimating, not exact numbers)... And you sure as hell know that Toews and Kane are going to be looking for a nice little pay day, we can't afford to use around 60% of the cap on 7 players and expect to ice a full roster. 2014-2015 would be very tight too, where 9 players make up 65% of the cap and that's without Campbell... with him we would be spending roughly 75% of the cap on 10 players.
Of course, the cap will probably go up, but with that contracts that will be signed between now and then will inflate as well, so using percentages is probably the best way of looking at it.
I'll take that extra $3-4 million cushion that Oduya brings in return for Campbell's offense... which he really never had a chance of fulfilling his potential to begin with in Chicago on the 2nd pairing. Defensively, I would venture to say he is even better than Campbell which makes him more useful to the Hawks for that price... IE: blocks shots, better on the PK, etc.. etc..