F/A-18E and F/A-18F Rhinos: What's the difference?
The only major difference between the E and the F is the extra seat and its consequences (lower internal fuel capacity, lower landing weight etc).


  Fuel Capacity internal: (F-18E) 14,400
  lb (6,530 kg) (F-18F) 13,550 lb (6,145 kg)


http://www.aerospaceweb.org/aircraft/fighter/f18ef/
(data and own sources on the bottom of the page)

It also has a lower "Carrier Bringback Payload".


  Carrier Bringback Payload F/A-18E: 9,900 lb (4,491 kg) F/A-18F: 9,000
  lb (4,082 kg)


http://www.boeing.com/defense/fa-18-super-hornet/#/technical-specifications