well first off is that you would probably need stronger lights to grow xenia than you would need for cheato. And I don't think xenia absorbs phosphates and nitrates. Also Xenia can actually spread to pest proportions.
xenia will absorb nitrates and phosphates, but wont do anything for fine particles becuase they dont have a functioning digestive cavity. But before you replace macroalgae with xenia, you have to take into consideration the growth rates of each