Question, you have two LT500's same Gearing. Sand Tires, swing arms , a arms, shocks  ect same rider weight on both quads shooting a 300ft hill.
One lt500 is making 70 HP and 46 ft lbs of torque, the other LT500 is making 65 HP and 56 ft lbs of torque.
which one would win (in the real world) sorry had to add that, what is more important when climbing a hill "Torque" or "Horse Power"

You did not supply enough information to make an educated evaluation.

The power curve that has the highest power AVERAGE through the RPM span that is defined by the gear ratios in the transmission will accelerate the best.  The engine with the highest peak power will have the potential to have the highest top speed on the hill if the hill is long enough and the gearing has been optimized. 

The shape of the power curve is what will determine which engine will win.  We can use calculus to evaluate the dyno curves that will perform best by using numerical integration or we can take it to the drag strip or hill and possibly add some rider error that could cloud the test results even further.

A dyno of ANY type is an invaluable tool when used by experienced persons that understand how they work and know the limitations of the tool.  Interpretation of dyno results and how the engines will perform in the real world also comes from tens of thousands of dyno runs and comparing the dyno test results with racetrack testing.  I have one chassis dyno and four engine dynos in house.  Selecting which dyno will be best for a particular project comes from experience. 

We work on a lot of engines that were built by engine builders that have dynos but we find common errors in their engine designs.  The design errors are a result of improper dyno testing procedures.  Test procedures MUST accurately simulate engine variables that the engines will experience when they are used for their intended purpose.  The instruction manuals and training sessions furnished by some of the dyno manufactures starts many of the new dyno owners off on the wrong foot.  Some of the new owners eventually develop test procedures that puts them on the right track while others continue the cookie cutter test procedures from there early training.  Unfortunately dyno manufactures are not seasoned engine designers, they just supply us with measuring tools.   Sometimes their lack of understanding of the types of engines we are building causes them to suggest the wrong tool and related equipment.