The only 'lack of power' from Axis pedals is due to lack of power in the player. They are as close to a direct translation of foot to drum as can be had and because of this they are unforgiving for sloppiness in play.
Many players will check them out in a store and find them lacking because they reveal the players imprecision then they spread the word of the pedals being 'weak'.
The reason why they 'feel' less powerful is because the moving parts are so much lighter that the 'felt' resistance to movement is so much lower. This resistance is known as 'inertia'. More mass, more inertia. More inertia means that you need more energy to accelerate it at the same speed, and this is why Axis 'feels' less powerful...because it takes less power/energy to play them than other pedals. The beater hits the head with as much or more energy than other pedals.
Because they are so different in moving mass and because of the direct linkage, new players generally need to get comfortable with them for a few weeks. When they get comfortable with them, they generally never go back to chain/strap drive pedals.