I have a SQL server instructor (Bell) who told me it does require some CPU cycles to resolve a name if it is not qualified with a schema name. Also, if you do NOT qualify the schema, what schema will be used? (I think, by default, the schema that contains the stored procedure will be the default schema rather than the default schema of the current user or the default schema of the database).

For these reasons, as a general practice, I always qualify database objects in stored procedures as two-part names.