rear brakes 12 or 13

[snappytravis]

I received a quote on brakes for the rear of 69 camaro, 760 for 12.19 rotors or 1600 for 13 rear rotors, Is there really that much difference to spend the extra 900 bucks for the 14 inch rotors? thinking about going with 13 on the front and 12 on the rear, what are your thoughts guys, also I see some of you just run manual brakes, looks to simple, do they work good?