[Mulv]

There is only one difference - leather requires maintenance and vinyl does not. If you use the car, which most do not, leather will not last as long.
Synthetics last longer than organics in the sun..
If you only plan to drive the car occaisionally and keep it in your garage most of the time then it doesn't matter which you choose..buy the cheapest. No one can tell plastic from leather anyway, and it is a kit car after all...

The semi-dry climate here means you still have maintenance on leather even in the garage..