Ah, the old tyre debate...
They are as bad as each other as far as i'm concerned.. pirelli's have got nothing in the wet compared to say a continental or uniroyal or yokohama.
And tbh the nankangs that got them their bad name were the EX500's which i don't think you can get anymore. They do Toursport 611's now and they are a world apart from the old EX500. And i have said many times before but i shall say it again, Nankang make very good tyres but the tread patterns are designed for much bigger cars and they just don't seem to work as well in this smaller size. Lots of highly tuned Supras, Skylines and the like use Nankangs because they are awesome.
And ultimately if you want good grip from a cento then the best route is a 14x6j wheel and a 195/45r14 tyre, and perhaps with enough power and on a track some 15x6j wheels but you really need some turbo or 16v power to not slow it down too mucch on 15s.