Function args: TEXT -vs- VARCHAR?

When writing (9.2) PostgreSQL functions, is it preferable to have text
or character varying args?

The tables the functions are updating/inserting into have character
varying columns.

I've used both in various places & want to unify.

Using character varying with an over length arg causes the function to
bomb out on calling, which seems the logical thing to do as the table
can't accept the data anyway.

Thoughts?
-- 
Craig Skinner | http://twitter.com/Craig_Skinner | http://linkd.in/yGqkv7