I bought some lavaterra becuase a neighbor had a well-behaved thing that went 6-7 feet straight up in about one square foot.
Then I planted two that sprawled out to a radius of 6-7 feet, 13 feet accross, and looked like day of the Triffids.
I guess that was "erect vs sprawling" more than it was size, but I had to move those monsters before they highjacked my house!
Size matters!