CSR 175 final spec: 5 speed or 6 speed

[AWL]

Having read all gearbox related threads on PH and other forums, I still can't make my mind up on the type of gearbox.
Here in Belgium the only gearbox options are the standard 5 or 6 speed boxes from CC, as we can only register factory built cars.
The car will be used mainly for road use, with the occasional track day.

Given the 'soft' use of the car, is a six speed gearbox worth the extra investment, or will the standard five speed provide the same fun and sensations?

[AWL]

So what's the difference between the ford and Mazda five speed then?
And which one is fitted to a new EU4 CSR?

[AWL]

Thanks LawrenceR

If the difference between the mazda 5 speed and caterham six speed is only 500 rpm in highest gear, I might as well go for the six speed (and buy some extra hearing protection).

Furthermore I think the six speed will provide more fun on the regular one or two hour blats on the b-roads. And since I will only be using the highways when I don't have any other option, I don't think the extra noise caused by the 500 rpm will be an issue.