I don't mean to be rude at all, but...the answer to your question is a simple matter of looking at the bars. Form follows function, the bullhorns allow for a more upright yet still mildly aggressive riding position--they are good for riding situations where you need to be looking around yet still riding hard(the city). Track bars allow you to get lots of leverage for hard pulls and to be aero as well, they are also generally tighter to the bike than road bars, letting you slip through smaller spaces. The downside is a lack of stability in lowspeed situations and less forgiving handling.