I would say go long tubes. IN essence you car will operate more efficently and if you keep your foot out of it gas milage should increase. Plus the sound difference will be very pleasing.
2006 Mustang GT in Torch Red
C&L Intake, Evolution Performance Tune, Borla Axle Backs, Hurst Shifter, 4.10's, JBA Long Tubes, Prothane Engine Mounts, Steeda UDPs, FRPP Charge Motion Delete Plates
84 Bronco, 302 C6 on 32 10.50's