The new island is not made from a base tile and seperate hills (like WIN). Instead it is a single mesh. This allows much more control over the topography and scaling. This means the new island is more accurately modelled on the real world dimensions and contours.
The island also has a new hi-res texture (4096*4096). This, combined with the fact the base is rendered as a vessel, means it looks a lot nicer than WIN.
Alpha Mesh and Texture available from Source.
This pic shows the difference between the texture rendered in Orbiter as a base object vs. as a vessel object. (top is base, bottom is vessel)
shot of the alpha mesh in AC3D
shot of the alpha mesh in Orbiter with TA1-1 on the tarmac
shot of alpha mesh with base plane in Orbiter with 5 TA1 at the proper location
shot of correction of shadows around alpha mesh by means of FLAG option in mesh file
shot of correction of curvature bug by means of repositioning hangars wrt. topo mesh
shot of placeholder mesh