It's just because the zone has finally upgraded to the clusterfcuk that is vBulletin 4, and they're both still running the pretty bog standard theme with only a few minor tweeks, like putting the various modules in slightly different places.

At least when I moved a site from vB3 to vB4 I put the effort in to make it not look as blaringly obviously just another vB4 site. But doing that does cause me headaches with the continual tweeks the developers love to implement with just about every update (and there are plenty of them!)