Warren,
Here is a comparison of
HP & Torque output by the various US spec 914 engines.
The
Acceleration Curves produced are also available.
That would pretty much cover the stock difference between the 1.7L & 2.0L. Keep in mind, however, that the 2.0 heads allow slip-in substitution of 96mm pistons & cylinders in place of the stock 94mm resulting in a 2056cc engine as noted by Eric... so that would be another possible advantage to the 2.0L. Lastly, the resale value of the production 2.0 will be higher (but then you would be paying more for it, so I'm not sure that matters much).