An interesting thread!
I have a new GT which I rather like - however I also have a DBR Aston and a 1980 Aston (amongst other things), so have a little experience of old Vs new.
I was very politely knocked off the waiting list for the Ford GT a few years ago and so started to look quite seriously at building a GT40 replica - or I should say, have someone else build one for me as I am truely hopeless with spanners. Whilst I have not driven the GT40, I have chatted endlessly with those that have - also at 6'3" it's a bit tight.
As luck would have it, I happened to find a brand new GT for sale and bought that instead. I have tracked it at Goodwood a few times (was also at Le Mans for the Classic) as well as taking it on jaunts through France - it's a very useable 598bhp (550 is a modest 'estimation' according to Roush!) and has incredible torque. As previously mentioned, it's also quite comfortable - runs cool, not too stiff and a fairly mellow V8 exhaust tone (I couldn't drive my DBR for extended periods - too loud!).
Would I swap? No. Do I love the shape of the GT40? Yes, of course. Is the new GT close enough for me to the GT40? Yes. I also like the fact that it was built by Ford rather than me.... Would I consider a 40 to have in my garage alongside the GT?
I'm not sure there's a valid comparison between the two - the GT40 is a raw track car, hot, mad, loud, stiff - wonderful!! The GT is a road car that's powerful enough to eat most things in a straight line on the track.
I'm not sure I've helped the debate!