Which car you think is better : Nissan GT-R LM NISMO (2015),Audi R-18 E-Tron Quattro (2015)or the PORSHE 919 Hybrid (2015)...

I have 600 Golds right now and I want to participate in the High Voltage Formula-E,so I don't know how much golds I'm gonna have left by the end of the month(when car on sale).
The Cheapest is the AUDI I believe at 475 GC,The others 2 are at 523 GC.

Decisions!?!