Why not just buy them both? I remember some people saying Pixar, Star Wars, Marvel, Minecraft, Bethesda etc. deals were all over priced or at least questionable at the time, but over time they all look cheap now (Bethesda remains to be seen but sure it will). If you price in the potential scenario where a competitor gets them instead and how that may play out, then it is probably even easier to justify.
Part of the problem with buying WB would be untangling all the existing IP deals that are probably in play, not to mention taking on assets that may not be in your wheelhouse (Movies, TV). 2K in that respect would be a more straight forward deal and may be more appealing in the first instance.