Looking at pictures of the 'kit' pipes, it looks to me as if they are 'thinner' than other after-market pipes (Like the jolly-motos) although fatter than the stock pipes... Is this right?
This suggests most of the power from the 'kit' configuration comes from the increased compression ratio - and that fitting the kit pipes to an otherwise stock bike would produce less power than fitting something like a jolly-moto or equivalent exhaust.
The shape of the kit pipe definitely looks like it is designed for a wide powerband (not sharp) which would explain why they rev-out better, they should also give better mid range.
All this leads to the conclusion that the jolly's will produce more peak torque than the kit pipes.
It also leads me to think that cutting down a set of jollys to make them shorter would produce more power than the kit pipes? (by shifting the jolly's greater peak torque up the rev-range resulting in more peak power) ... Of course the extra compression might damage the engine unless higher octane fuel is used (higher than AvGas that is)