In reality the cast iron calipers are only about 10 pounds, so the real weight saving is only about 5 pounds per caliper. In return, you have all the problems that aluminum brings with it. Ask Corvette owners. What rotors are you running?
Perhaps caliper vs. caliper you don't save a ton but everything else that surrounds the brakes is larger too. Those integral rotors are super heavy, larger ball joints, UCAs etc. It all adds up.
