I can see your predicament! I would say to not stress about the sofa color too much. Once it’s in the room, the shade differences won’t seem as drastic as they do online.
I recommend going with the darker Wayfair option. You can decorate wth throw pillows in various shades of white, and you’ll hardly notice the difference from the Z Gallerie option! Plus, you’ll have saved $1500, which is always a big bonus!