Power is irrelevant when the numbers are within ~40% of each other. Some of it depends on luck, some on formation, and some on your armor and rune setups. The player with the best setup will win most of the time, but that player doesn't have to have more power than the other one.

For instance, Morale grants zero power on its own, but adds a fair amount of real and noticeable power to PvP fights. If you take out two or three enemies before they even get a shot in, you've just mitigated a ton of damage. This is just one example of power numbers not matching up to actual fighting strength.