What would really determine the engine noise under normal conditions (not full throttle) is the throttle setting necessary for obtaining the wheel torque desired. The seat-of-the-pants feel (wheel torque) for power/acceleration is the engine torque at any particular speed coupled with the final drive ratio (transmission + rear end).
If you compare the torque curves of the two engines (assuming a similar final drive ratio), I doubt you will find significant differences anywhere along the curve (1000 - 2500 rpm) that would cause a noticeable difference in engine sound. Any difference in torque between these two engines at normal speeds is probably negated by the difference in weight between the V6 and V8 vehicles (4300 vs 4500 lbs).
The displacement difference between these two engines is not that important since they are both truck engines and designed to give alot of low-end torque for towing and lugging.
The old saying that "there is no replacement for displacement" is talking about the potential for getting maximum horsepower out of an engine when you are comparing a 5 vs a 7 liter engine. This is not very important for these truck engines with very similar displacements (~15%).
JMHO