I know the 6 speed box is sturdier, but that's obviously as it was built with the extra power in mind, but I've never really seen the need for extra gears on road cars. This isn't a Subaru thing either. How many of these luke warm hot hatches and super minis come with a gearbox that you'll be forever stirring? When they're busy changing gears I'll be enjoying a spot of torque down the rev range.
How if you give me a Supercar it's a different story ....