Ah... yes I've seen people make this mistake so many times it's lost any humor it once had...

Hagendis Hit:
Only hits a single target, but does the most damage. This is the sort of skill you use on a boss, or when you need to take down an enemy right away.

Hagendis Beating:
Hits two targets (in a line), great for weaker mobs, or when you have multiple people using this skill it is very useful against stronger mobs.

The same general idea goes for the following fire element physical skills:

Sword Awn Hit/Beating
Five Star Hit/Beating
(Not sure about Fire Wave Hit/Beating)

Please note: I only have a fire element warrior, so this is all I know from experience. But it's good experience, trust me ^^