Which is the best diamond clarity?

SHIREE'S ANSWER:

The best diamond clarity on the GIA clarity grading scale is FL, but honestly you don't really need it. Not even close! While clarity is important, the scale isn't a linear distribution - so the top grades from FL, IF to VVS1 and VVS2 are an elite, small percentage of diamonds. To the naked eye, a VS1, VS2 and in some cases SI1 and SI2 will look identical without magnification. Clarity should not be confused with sparkle and brilliance, which is also determined by the raw diamond material and the cut of the polished diamond. Only on the very low end of the clarity scale such as I1 (P1) to I3 (P3) will visible brilliance be affected.