Why Would I Want To Use Big Weapons?

So I dusted off my Wii with MH3. Never played a MH game before but it looked fun. 
 
I'm probably 2.5 hours in and I'm thinking to myself "Why the fuck to these giant, slow, weapons exist?" 
  
I don't know if I'm just ignorant to this series, but why would I want to walk around 10x slower than my enemies and just swing once or twice and then the monster will evade backwards and I can't get in range of him. In the end the only good weapons are the small and quick swords. Ugh, the big swords, the maces, the lances, all awful. I don't get these slow, clunky, but powerful weapons.  
 
EDIT: Grrr, I was in the MH3 forum and clicked "add new topic" but somehow it's still in general.

Good question. I played a little MH3 and couldn't stand the big weapons; they were just way too sluggish. That's probably just because I suck at the game, but the fast weapons certainly felt much easier to use (and overall did more damage, because I'd actually HIT WITH THEM sometimes)

I can't speak for the new slash axes and w.e but the old greatsword is very, very good in the right hands.
 
In the psp version the greatsword can be charged, depending on the length of the charge you can sometimes do enough damage to break the limb of a monster in one hit. The greatsword is all about positioning and timing - trying to charge to maximum before the monster can attack you. Once you learn to use the greatsword all the other weapons will feel totally weak in comparison.

Different playstyles suit different people.  Some people like being slow but powerful.

" Different playstyles suit different people.  Some people like being slow but powerful. "