Sometimes it is faster, sometimes slower:
In[5]:= Table[((PlanetData["Mars",
Dated["HelioCoordinates", Today + (Tomorrow - Today) #]] & /@
Range[7]) // Timing)[[1]], 20]
Out[5]= {6.42188, 7.875, 8.78125, 8.59375, 6.84375, 6.84375, 6.89063, 6.8125, 7.125, 8.79688, 6.79688, 6.79688, 6.79688, 6.8125, 7., 7.51563, 7.1875, 6.82813, 7.71875, 6.70313}