Is this your first visit to Sicily Needaholiday_13?
Are you anticipating a beach holiday?
If not, you would surely look to base in an area that would offer more sites and attractions than small coastal villages.
The Michelin Green Guide ranks destinations, and may help you decide what you would like to see and do.
Your location would also very much depend on where you would arrive and depart Sicily - Catania is the preferred airport for Southeastern Sicily, but if arriving in Palermo, Southeastern Sicily isn't the most convenient area to reach, and with only a week, you would want to minimise your driving time.