Even if weight were equal, the steam engine would still likely outpull the JD the way they were hitched.
To show a true (fair) pulling ability, hitches must be level.
When it comes to brute pulling HP dont mean squat. Weight (traction) is king as long as you have the torque to move. You could couple a 8000HP dragster to a simple 40HP tractor offroad and the tractor will win everytime.