Even though the percentage searching for axis games is indicative and symptomatic of the axis being op (especially in team games). You can dress it up anyway you like (people prefer the German units/the factions are more fun to play/etc), but it simply comes down to, that for the average joe (90% of the coh player base) the Axis provides a far easier way to win.
Bringing up percentages is still irrelevant when talking about balance. It does not support your argument at all, because it says nothing about units, says nothing about strategy or design of factions, it's just pointing at numbers outside the game.
For example, If you are going to end your argument with "look at the percentage that proves it!" On a topic about whether or not Stuka rockets are overpowered then your argument is already invalid, because it has nothing to do with the rockets and it doesn't prove your point.
If you want to show that Axis are easier to play then say "It's easier to play because this..." instead of "nobody wants to play allies anymore, therefore axis is OP." That just doesn't make sense.
If you want to bring up percentages based from past experience, well from my past experienced when Katyushas and ISU152s were overperforming to a point to which it was very easy to win as allies a few patches ago. It was still easier to find a game as allies than it is axis because the percentages still is mostly Axis, so maybe the percentages doesn't mean that much when it comes to balance. Maybe the only way to make players percentages even up is to make Allies overpowered if you think balance is based on players percentage.