G-Max, Double Cyclone and Eco Flush all use a siphon jet flush.
The G-Max uses 1.6 gallons and the rinse goes straight down the bowl.
Eco uses 1.28 gallons, and the rinse goes straight down the bowl
Double Cyclone uses 1.28 gallons now, and the rinse circles the bowl.
Basically, the same amount of water is going through the siphon jet, the difference is in the rinse, the direction it falls.
They are all pretty similar.