To an electrical engineer it may seem obvious from the specs, but you may be confused because no power ratings are provided and the designations 'High Power' and 'Low Power' are not explained. To understand the differences you need to know that,
Electrical Power: Watts = Volts x Amps
Mechanical Power: Watts = Torque (N.m) x rotational speed (rad/s)
At 6V the 'low power' motor draws 0.25A free running and 2.4A when stalled, so its power consumption ranges from 6x0.25 = 1.5W to 6x2.4 = 14.4W. The 'high power' motor draws from 3.3W to 39W.
So the 'high power' motor can draw more power than the 'low power' motor at the same voltage. But is this what they mean by 'high' and 'low' power? Their customers are probably more interested in how much mechanical power the motors can produce, rather than what electrical power they consume. This information is not provided either, so we will have to analyze the specs to determine which motor is truly more powerful.
At no-load (free running) a DC motor produces maximum speed, but no power because torque is zero. At stall it produces maximum torque, but also no power because the speed is zero. Maximum power output is achieved at 50% of no-load speed and 50% of stall torque. A typical graph of speed vs torque, current, power output and efficiency looks like this:-
So at maximum power output the 'Low Torque' motor should produce 50/2 = 25oz.in at 170/2 = 85rpm, while the 'High Power' motor should produce 45oz.in at 140rpm.
Clearly the 'High Power' motor is capable of a propelling a larger vehicle at higher speed. However its minimum current draw is over twice as high so it might be less suited to a smaller vehicle, and the stall current is much higher so you may need a more powerful speed speed controller and battery.