Why is HV better?

[xcntrk]

Hey all, I’m trying to better understand motor selection (kv), versus wattage and voltage, to determine which motor is best suited for my rig. I’ve been using BrianG’s calc and don’t understand why higher voltage coupled with lower KV motor is a more ideal setup? Or at least that seems to be the consensus around here.

For example I crunched the following two configs.
The first is a 1521/1y on a crazy 8s (way too much power for me, just an example):

Differential Ratio:  3.3076923076923075 
Transmission Ratio:  1.7222222222222223 
Other Ratio:  1 
Spur Tooth Count:  51 
Pinion Tooth Count:  20 
Total Voltage:  29.6 
Motor KV:  1577 
Tire Diameter (inches):  5.75 
Tire Ballooning (inches):  .1 
Motor Current Draw:  75 
Motor coil Ω:  0.008 
Spur/Pinion Ratio:  2.55 : 1 
Total Ratio:  14.52628 : 1 
Tire Circumference (inches):  18.69 inches (474.79 mm) 
Total Motor Speed:  45733 RPM 
Vehicle Speed:  55.73 mph (89.52 km/h) 
Effective Speed Rate:  1.88 mph/V (3.02 kmh/V) 
Estimated Adjusted Speed:  52 mph (83 km/h) - 7% loss 
Effective KV Value:  1545.03 
Motor Torque:  0.33 ft-lbs 
Final Torque:  4.86 ft-lbs 
Final Power:  2220 watts (3 HP)

The above produces a top speed of 52mph with 4.86ft-lbs torque and overall 3hp with the motor spinning at a comfortable 46k rpm. The next config is a much more realistic 1515/1Y on 6s. (Great config for me as it doesn’t require a HV ESC, plenty of 6s compatible out there):

Differential Ratio:  3.3076923076923075 
Transmission Ratio:  1.7222222222222223 
Other Ratio:  1 
Spur Tooth Count:  51 
Pinion Tooth Count:  20 
Total Voltage:  22.2 
Motor KV:  2200 
Tire Diameter (inches):  5.75 
Tire Ballooning (inches):  .1 
Motor Current Draw:  110 
Motor coil Ω:  0.006 
Spur/Pinion Ratio:  2.55 : 1 
Total Ratio:  14.52628 : 1 
Tire Circumference (inches):  18.69 inches (474.79 mm) 
Total Motor Speed:  47388 RPM 
Vehicle Speed:  57.75 mph (92.76 km/h) 
Effective Speed Rate:  2.6 mph/V (4.18 kmh/V) 
Estimated Adjusted Speed:  53 mph (86 km/h) - 8% loss 
Effective KV Value:  2134.59 
Motor Torque:  0.35 ft-lbs 
Final Torque:  5.11 ft-lbs 
Final Power:  2442 watts (3.3 HP)

This setup produces 53mph top speed, 5.11ft-lbs torque and 3.3hp with the motor spinning at a comfortable 47k rpm. Nearly identical figures (with more torque too) on less voltage.

So I don’t understand why the higher voltage setups with larger motor (lower KV) is more ideal?

Please help set me strait, obviously I'm missing something???