I currently own an '04 GX470, '15 GX460, and a '15 4runner Limited (for sale), and I've now driven the 460 enough to develop some opinions:
-GX470 is an excellent vehicle, power is strong off-idle, throttle calibration is fine from factory
-5th gen 4Runner is an alright vehicle, it's not built as well as the 11 year older GX470, thinner sheet metal and glass, less insulation, throttle calibration is horrible from factory, Sprint Booster made a big difference in how it drives. Changing the throttle input response makes it feel much more powerful, the trans shift points are also modified as it thinks you've pushed the pedal further, the entire powertrain is more responsive and less gutless feeling.
-GX460 is so smooth compared to the 4Runner, where the V6 is thrashy the V8 is silky, everything you touch is nicer materials, you can tell they are the same vehicle underneath, but it's WAY underneath. The GX460 compares more directly to the 4Runner than the earlier GX IMO, the older GX is it's own thing, and it's great.
The GX470 I've never felt needed a Pedal Commander or Sprint Booster, but the GX460 could benefit from one, and it's on the list. On a vehicle that needs it, it transforms the driving experience in a way that "push harder on the gas pedal" doesn't accomplish, it allows access to the power you purchased without having to feel like you're beating on it. Fuel economy is unaffected by these devices, that all comes down to you as the driver.