I have to retract my last comment, as it seems we're in agreement.
I too am a bit unsure wether Alto was shooting to kill, but he was for certain taking the fight way more seriously than Ozma was.
As for performance differences between the machines, they might actually be monstrously huge or not so big at all, but it doesn't actually have any bearing on the original question: "Did Ozma in the VF-25S pwn Alto in an upgraded VF-171? OR where they evenly matched?" It does have bearing on potential followup questions "Would the result have been the same if they were piloting the same machine?". Small but important difference