Allegedly better gas exchange using the air stones.
According to the math, definitely so. More surface area and slower rise. Now, is it significant? I'm not sure.
Another benefit is less backpressure I believe (not certain and not spending time to look it up right now).
For me, I've never used airstones with sponges. I've thought about it, but never pulled the trigger. I was curious to see if there would also be a stronger pull of water through the uplift tube using air stones.