The Apex and Attak will pull 14-16 mpg, the Vector and Rage will pull 18-20 mpg.
IMO, if you are an aggressive rider you will like the Apex/Attak better. It has more of a rider foreward position and the taller bars make it really easy to ride fast on. Plus, the EFI system is really nice. No choking, no messing with the throttle. All you do is turn the key and once the engine fires up the computer does everything for you.
If it were me Id go for the Attak. Granted, you give up some fuel economy but the Genesis 150 FI engine is a work of art.
If you are buying new you might want to consider waiting until February and ordering an '08. Rumor has it that Yamaha is putting EFI on the Genesis 120 (the motor the Vector, Rage and Nytro use) and will be putting it in the Deltabox 2 chassis (the chassis the Apex and Attak use).