V8 supercars must be harder to drive and I like the fact that it merge some european auto-racing culture and american (V8 inside).
However must tell that WTCC is a bit better because it is a worldwide championship where driver from lot of country are racing. Several manifacturer are involved whereas V8 supercar is only an australian championship where the majority of the driver are australian...It would be fun to see how many non-australian (+new zealand...) have raced there...maybe Yvan Muller.
So it is hard to compare WTCC and V8 supercar. I prefer V8 supercar spirit with some sprint and endurance races, big engine, ... but WTCC is really another thing. It is as comparing Le Mans and Formula one or nascar and GT1 ^^ Could be better to compare BTCC and V8 Supercars, both are almost on the same scale