They both average out at about 1.28 gallons.
For cleaning and for the boys, get the CST744EG
That model has an elongated bowl, a little easier for the boys to hit the bowl.
Sanagloss, a smooth finish, for less cleaning
Get the softclose SS114 seat, no more slamming seats.
Below are a few of the toilets I'm selling.
TOTO with Sanagloss on the left, Gerber Ultraflush, and Caroma dual flush on the right