Bigger throttlebodies are a complete waste until you are well over 300hp. It simply isn't a restriction compared to the heads or exhaust. Same goes for everything else in the inlet tract.
The "better throttle response" is simply physics. A bigger TB is going to allow more air to pass at a given pedal position. More air is more power, but as you get close to wot you lose velocity, which can actually cost you torque. So yeah it feels stronger, However it isn't going to give you any more power at stock levels. People that "see" a power increase nearly alway have significant mods already, or had a tune applied at the same time. Most of the time its a tune that actually is the source of the boost in power.