In 1798, a new Liberty Head hub punch appeared for the Draped Bust large cent. The most obvious difference between the old and the new hub is the addition of two prominent curls to the new hub: one in the hair near the shoulders and another in the hair to replace the softer curl below and to the left of the ear. The new style was used on all Draped Bust Large Cents through 1807 with one exception -- when an old 1798 obverse was overdated to 1800!
According to the PCGS Population Report, the 2nd Hair Style is slightly more common than the 1st Hair Style, though there are more Mint State examples of the 1st Hair Style. The finest 2nd Hair Style certified by PCGS (as of May 2011) is a single MS65RB.