Sometimes my first shot is really the best. Other times, shooting at other angles and distances opens up more possibilities in my mind that perhaps had been overridden by the concept I had before pressing the shutter button the first time.
At any rate, I have found that 1) Usually the first shot gets it, but 2) Often, a later shot either does it better, or from an equally interesting viewpoint that makes it worth the extra time and file space.
So, as a rule when I have the time, I take the first shot and then look for others that might equal or surpass it. Sometimes it pays off, sometimes not, but in case it did, I have it on the CF card.