I think you read Dazco's post over at Triumphratnet. He is very enthusiatic and in truth I am thinking of trying the seventeen toother.
It has to add something on the high end but in terms of strict torque it has to take just a little bit off the low end. But I bet it is not all that noticeable for a one up rider. Add a pillion and first gear may seem a little bit lacking .....but I bet not much. May not be noticeable at all.
Most of the posts I have read in this here August forum are enthusiastic as to the use of the one tooth up sprocket.