It really depends on the player. I would assume new people tend to pick Tac most, though - just based on the idea that they think it's more powerful from its name - and that Science is, likewise, picked least, also based on on the name and what people might think it does in play.
for me it comes down to color. Command officers wear red. (at least on the fed side) so I run a Tac.
Except before TNG, when everyone wore Red jackets and Command wore White collars, and before the Wrath of Khan, where Command wore Blue-Grey or White, or Beige on away missions, with White patches, and before TMP when Command wore Green, or Gold (or more accurately, Green that photographed Gold).