I have friends visiting soon who want to hire a car and explore a bit.  I recall there was both approval and condemnation of certain companies but can't remember which was which.  I know that some companies insist on you buying and over-priced tank of fuel to bring the car back empty (even though you can't get through a whole tank in the duration of the visit) whilst others do not. 

The options seem to be: 
Hetrz/Advantage
National/Europcar/Alamo or
Goldcar

Any preferences?
Thanks
Mike