The Alfa.
Next year or the year after, or maybe the year after that, Ferrari will replace the 430 and it will be yesterdays flavour of the week, just like the 360 is now, and the 355 was before that. However, the 8C is the first Alfa in that kind of league since the SZ, which was produced 20 years ago. I don't see it being replaced any time soon - it will be iconic and special for many years.
Without doubt, the 430 is better when it comes to lap times. I would love one. But I'd feel a like a bit of a burk every time I drove it to the track (although at least that one has a roof). I'd rather have an 8C because it's a little bit more special than 'just another 430'.
Any fool can buy a 430 - it takes a true connoisseur to buy an 8C.