Certainly Thunderbolt can carry more Data than type C. WD19TBS is a more powerful dock works on higher speeds compare to non TB version.    But main consideration is your use case. Cause you are paying 75$ extra and loosing a headphone jack in TBS. Both docks will charge your computer, both will let you plug several monitors and peripherals. TBS will let you plug more higher resolution monitors at the same time.   So all comes to How many monitors are you looking to connect, what resolution and refresh rate they are. What Devices will be plugged in to    Check display resolution section on both dock's manuals     WD 19 type C  
Since the XPS 15 9510 comes with 2 Thunderbolt ports, is there any advantage to buying the 'Dell Thunderbolt Dock - WD19TBS' over the 'Dell Docking Station - WD 19S 180W'  for use with that laptop? Thanks  
Docking Station for XPS 15 9510