Which Toto Aquia model to buy?

I am very interested in replacing my two american standard toilets (vintage 1956) with the Toto Aquia. There are three models: CST414M, CST416M, CST464M. How do i choose between them / how do i decide which one is appropriate for my bathroom configuration?

I'd appreciate any help. thanks.

All of the Aquia toilets are dual flush, elongated, about 27-1/4" long.
The I and the II have 15-1/8" high bowls.
The III that I have is 16-1/8" high.
And then when you add a seat, it adds about an inch.

The I has the bigger trapway, and has a little longer install time.
The trapway on the II and the III is similar.