BathMate HYdroMax 7 vs HydroMax9

Hey Folks,
Erect, I’m about 6.5 - 7 x 5.5. I know it suggests Hydromax7, but I was wondering if there’s any reason NOT to go for the Hydromax9. The base of the cylinders is the same for the Hydromax7(wide) and the Hydromax9. So I’m thinking it wouldn’t make a difference.. Any other ideas?

Thanks