Same with me. In a duel there is really no reason to take more than 25% fuel if the intent is to fight and not try to run the other guy out of fuel.
ack-ack
And here we have de facto "personal preference" enforcement, where you are subjecting what you deem as necessary, due to your style of flight, on another, regardless of their style of flight.
You see, you could load 50% fuel if you feel that we're going to try to outlast you, but you would complain that you're not as maneuverable as someone with 25% fuel. So, logically then, we would choose perhaps 50% fuel for most planes, but then people would complain they couldn't turn them as well as they could with 25% and that they're at a disadvantage, even though the other guy is identical.
Therefore, we implemented pilot's discretion. Nothing more, nothing less.
That being said, the reason why we didn't use a flat 25% or 50% value was because of flight time. Although rare, some fights truly last 10-15 minutes, so we didn't want fuel being an issue or cause of a loss. Changeup actually ran out of fuel in an LA-7 fight, and we came close, even though he was actually engaged the entire time.
Now, with that, perhaps the most neutral approach is to use a fuel loadout that allows for X number of minutes (the smallest fuel loadout that allows for a set flight time).
This, however, brings back up having to review every film and every fuel loadout... and for what? In the end, it's all solved by pilot's discretion.
Setting a time limit would be far more effective, though judging who won or lost if the time ran over would require some solving.