Coplanar waveguide vs open space?
Like the comments say, the Sparkfun layout is a microstrip layout. Microstrip is a waveguide where the return path is on the ground plane beneath the signal path. Whereas coplanar waveguide is a waveguide where the return path is (predominately) on copper regions in the same plane as (coplanar with) the signal conductor. 

I think your design is better than Sparkfun's.

The benefit of coplanar waveguide in this design is that it allows a narrower trace which matches the pad dimensions better and doesn't need a neck-down before readhing the antenna pad. 

In other situations, microstrip might be preferred because a wider trace will have lower resistive loss, or because it's impractical to maintain symmetric ground regions on both sides of the signal trace.