The power of magic

[Mac]

No: HPFGUIDX 55642

Hi
This is my first post to the list, so please forgive me if I am 
raising a previously aired subject, but it is one that interests me.

What, in Rowling's universe, qualifies a wizard to be powerful?

In most fantasy novels, a wizard's power tends to be a function of 
their ability to weild powerful spells.  That is, the more powerful 
the wizard, the higher the "calibre" of the the ammunition s/he 
uses.  Yet in Rowling's universe, the entire gammut of spells seems 
to be available to anyone, its just a matter of saying a couple of 
words.  So if Dumbledore or Voldemort are the most powerful wizards 
of their time, what makes them so - more than, say, Hermione, with 
her focused intelligence and considerable drive?

As I say, if it's been raised before, please feel free to consign it 
to the bin, but as one who enjoys writing as much as reading 
fantasy, its an interesting and relevant topic for me.

Mac