a 300zx TT????? seriously? did you get stock in the 1990s???
all kidding aside. thou i used to love the 300zx back in the day, i would go with the bmw.
my neighbor bought a 300zx TT about a year ago for his 16 yo son and the poor guy hasn't been able to drive the car because it is always broke.
the nissan is just way too old to be compared to a 335 specially if you are trying to get 400hp out of it, just the $ and time you would need to invest is not worth it to me.
good luck with your choice.