Basic organization question

[Tommy Kelly <tommy.kelly@verilab.com>]

I can see that TODOs can be organized using tags, or categories, or
files, or simply subtrees (or several of those). Is there an obvious
choice? 

All I'm really looking for is a basic organization, to let me "group"
tasks of different broad functional areas -- accounting, recruitment,
IT, and so on.

And I like the idea discussed in http://orgmode.org/org.html, where
tasks get captured into a single refile.org file and then later moved
about into their classification homes.

But of those various ways of classifying, is there one to be preferred?

thanks,
Tommy