1794 Large Cents can be found with three major obverse types: Head of 1793; Head of 1794; and Head of 1795.
The Heads of 1793 use a device punch from the 1793 Liberty Caps. These usually have a double chin and the head is not as tall as the Heads of 1794.
The majority of 1794 Large Cent die varieties are of the Head of 1794 type. On these coins, the bottom curl is shaped like a distinct hook. Hair details vary because of hand-finishing.
Technically, the only true Head of 1795 is Sheldon 72 (which uses the identical head of Liberty punch that was used in 1795. However, Sheldon 67 through 71 (inclusive) are also categorized as Heads of 1795. On Sheldon 72, the bottom curl is a short stub. On Sheldons 67 through 71, the bottom curl appears as a closed (or close) circle.
As expected, the 1794 Head of 1794 is a common type, though Mint State examples are scarce and valuable.