The 4.7-liter V8 is a fine motor. It has obviously proved itself in reliability. I've driven many 00-06 Tundras with the 4.7 (Both 4-spd and 5-spd combinations) and the truck has plenty of power for the average driver. Not everyone hauls or tows near their max limits. One thing Toyota has always done great was tuned their motors for low-mid range power.
I got the 5.7/6-spd combo because I'm coming from a fairly large 7.3 Powerstroke Diesel and I'm use to the torque + I need it to make me feel better about spending $40k on a truck

I will be honest and say that I've never really liked any motor that Toyota has produced here in the US, (Yes not even the 2JZ Supra TT motor) but all that has changed because this 5.7 is an ANIMAL. Pulls strong up top, great low-midrange...I can't complain at all. If Toyota tuned this motor for a sports car it will FLY.
Regardless of the 4.7 vs 5.7, just enjoy your truck. They both get you from point A to point B in Tundra fashion! :tu: