I think in general people give too much credit to the shifters for the "smoothness" of the shifting. The shifter just pulls and releases cable. How well the cables are installed and routed, as well as the adjustment of the deraillers makes far more difference. The front shifting is also going to be greatly affected by the chainrings, the profiling of the teeth, the ramps and pins, etc.
Now, how many people are really running a completely homogenous group? Is that crank really 105 or some FSA thing? Etc, etc, etc...
They usually come with FSA Vero cranks.
I never used Tiagra shifters so I can't comment on them.
Both my Tiagra equipped bikes used Sora shifters.
When I speak of how smooth Tiagra is, I am referring to the derailleurs specifically
(especially with my Ultegra SL crankset that made a huge difference in front shifting from the FSA).
In the U.K. they have full Tiagra bikes.