Difference , hmmmm, slight in the city only...... but, not allot and that would depend more on how you use your truck on a daily basis.... the difference (in real world driving, not DOT or NHSTA standards) is negligable IMHO. Go with the truck you really like and has the features you want..... if fuel consumption is a concern at all, you shouldn't be looking at any truck really....... if it makes you feel any better, our new 5.4 Screw gets better milage than our older Nissan Pathfinder and it only had a 3.5 V6, LOL.
2010 XLT Screw 6.5 box XTR pkg, 5.4, bike hauler
2010 Mazda 3 Sport, Black mica, commuter duties
2008 Kawasaki ZX-6R - race ready (track duties)
2002 Honda Foreman 4X4, 26`ITPs, mud toy