The 350Z will be more simply because it is a "sports car". The MINI will be less, how much I do not know. There are online insurance quotes, but I don't know any site offhand that do that. If you are male, under the age of 25, and live in the US, the insurance won't be cheap either way.
To give you an idea, I am 23, no tickets, no accidents, good student, on parents policy... and paying $3,000 a year right now. It was $3,300 until I got my grades this semester, they gave me a $300 discount for that. Woohoo
