Meh, I think McCollum is the better player, but in the role either would have here....
I'd much rather have Fournier for money than trade assets, he's as good a shooter (maybe better) which is the primary concern, he's got height so he's easier to hide on a no-offense wing/big than McCollum.
McCollum is good, I'm not sure he's significantly better than Fournier, particularly if it's as a 3rd option, I wonder how much of his value comes from being the 2nd option on a team that plays no defense and where the 1st option has insane floor gravity.