yeah I would have to lean towards the F50, the turn in is supposedly incredible and in my opinion it is one of the best looking cars ever made. I do agree that the F40 is not so much of a Ferrari, with the added turbos. I think the best thing would be to have a F50 GT...now that would be simply amazing..here is a link to a site with picutres and some of the info
http://www.fast-autos.net/ferrari/ferrarif50gt.html