awsome good question
i think we got apples and oranges and peanuts all mixed up
and the example just was close enough to look right
im shure some smart bastard can anser this correct and we wont know what the hell happend
i just look at the 2 kinds of weight that make sense to me spinning mass (tires and shit)
and payload (people seat spare tire)
hp is and old school measurement and is open to a whole new bitch fest
i use mechanical and i think its the ability to move 550 pounds one foot in one second or so

i would just weight the bastards and pick the lightest package
where the weight placed on the spinning mass is all the same if the weight is the same and you need x amount to move it
if its 5 feet long or 6 inches the leverage will work if the weight is the same

will you notice 3 pounds i guess it depends on you
there are other things that will impact it more