There is room for both IMHO remember you are comparing a stretched +4 chassis in original Maurice Owen model +8's.
One of which I ran for 4 years in 3.9 Ltr engine format and thoroughly enjoyed.
The new 8 is an Aero chassis and essentially an Aero in albeit modified Traditional clothing, it appears to me aesthetically pleasing (trad +8 on steroids) but I'm a lifelong fan of the marque so probably not very objective.
So would would I kick a new 8 out of bed ?
Definately no, to me this developement of the +8 is a far more exciting and emotive avenue than the M3W.
I have yet to try out a new 8 but it must be rawer than a rare steak, stainless shovels and excrement spring to mind.
If you hanker for the narrow bodied/Moss box here is a nice one complete with FIA papers and about 20 big ones less compared to a new 8 !
http://www.carandclassic.co.uk/car/C354496 Wishing you all a Happy New Year