Are you asking about buying or driving?
If it's buying, then Pesky all the way.
What's the point in buying an Audi R8 for 4.5million Cr when you'll win one as the prize for Sarthe I 24hr race? (which you could do in the Pesky!)
Driving is a matter of personal taste, I've driven them both extensively and would be hard pressed to chose a favourite.
The Pesky is exceptionally fast, has great handling and is very, very frugal with it's tyres.
The Audi is also exceptionally fast, handles well but isn't as conservative with it's tyres as the Pesky, but still seems better than many other Group C / LMP type racers.