If you are comparing on the Butt Dyno, gears are big! THey wake up the way a car feels, but dont necessarily make it much faster. Traction will become a big factor with the 5.0L where the V-6 just wakes up a bit. If you are looking at 1-1.5 seconds in the quarter difference, that is huge, but feeling it in your butt may not be as recognizable. Remember the 5.0L are smooth, the tune will wake up the feel of the power more so than it does in the V-6. Although I personally feel a true performance pony car is a V-8, the V-6 performs pretty well, but there is no comparison stock for stock or equally tuned/ geared. Good luck on your decision.
2011 Roush Stage 2 Convertible Race Red with painted gloss black stripes, Charcoal Interior-Roush # 11-0306
Bama Tuned, Roush Front and Rear Brake Kit, Roush Exhaust with Square tips, 20" wheels, Roush seating with Red stitching
Roush Billet Grille matching lower 3 piece, Matte Black side and top stripes, White Face Gauge cluster, Convertible Light Bar Purchased 27Dec2010
Dyno'd 401 HP/ 390 Ft lbs at the wheels