I am guessing that your V-6 probably had an aftermarket exhaust system, unless it was built in the last few years? I can attest to the aftermarket exhaust drone from my 2000 GT; the aggressive sound was great rowing up through the gears but at 70-75 mph it could get tiring, especially on a long road trip. My '13 5.0 is stock (for now), and while it sounds quite hearty when accelerating, it is relatively quiet at speed for what it is and does. So if you have a stock exhaust system, you'll probably have no cruising speed drone problems. With the aftermarket, there is a lot of variation among brands - some are better than others.
As far as the V-8 vs. the V-6, the V-6 is no slouch (especially the 2011+). But if you're into torque and don't mind the somewhat higher initial cost, insurance, and fuel expenses, the V-8 is a lot of fun. My 2000 GT had "only" 260 hp and about 300 lb-ft of torque, but it was an absolute blast to drive. Nothing quite like a V-8.