I don't have an answer for you as I don't have a comparison. I'm waiting for the truck that has my EcoDrake with sanagloss to come in. Get this: my Toto is stuck in Kansas...oh the irony. "I'll get you my pretty and your little dog too!"
My understanding is that the flapper on the Eco (1.28 gpf) can be modified to turn the toilet back into 1.6 gpf Drake if needed. That's my back up plan and why I decided to give this a go. If it works as intended I plan to buy two more.