A block is a discretization of the continuous track, and in track-space, your absolute "GPS" location isn't relevant -- just where you are on the track.
The on-vehicle location detector ("GPS") is essentially a cost-effective alternative to having infinitesimally small, fixed blocks.
The benefits are equivalent: the tradeoff is between whether you want to spend money on maintaining fixed trackside infrastructure, or more advanced equipment inside on-track vehicles.
A block is a discretization of the continuous track, and in track-space, your absolute "GPS" location isn't relevant -- just where you are on the track.
The on-vehicle location detector ("GPS") is essentially a cost-effective alternative to having infinitesimally small, fixed blocks.
The benefits are equivalent: the tradeoff is between whether you want to spend money on maintaining fixed trackside infrastructure, or more advanced equipment inside on-track vehicles.