One benefit is the tool not unloading the design every time you perform a new operation.
GUI
Read RTL, Elaborate design, unload design database, load design database, Synthesis, unload design database, load design database, implementation, unload design database, load design database, bitstream generation, unload design database.
Tcl
Read RTL, elaborate, synthesis, implementation, bitstream generation.
On the same design the Tcl version runs much faster, you would have to run with the GUI version on an SSD to get reasonably close to the speed of the TCl version, which never unloads the design unless specifically directed.