Ok, here it goes, this is a direct quote from one of my friends over here in Kiwiland (so pardon grammar etc, as I didn't have time to correct it much), he has both a 350z and an Evo8 and does his own mechanical work. So if you are a present or past owner, don't shoot the messenger, just trying to be helpful.
"Evo uses more gas than the z. My z was really efficient when it was stock easy 10km/l average and 13km/l+ long distance trip probably because of the gear ratio 6th gear is much taller in the z.
350z is a far better car then Evo. Evo is just fast tin can ride. It's just a typical 90's jap car.
The chassis is so old, needs a lot of braces to support the chassis, just like silvias etc, but evo are much faster than 350z there's no doubt. But not necessarily a better car just like comparing civic type r to accord euro for example civic type r is much faster car, but a tin can.
Build quality is just horrible. Evo's retail 65k (NZ$) or something i think its cheap for its performance
but its build quality is just like those under 40k jap cars, so plasticky empty behind the panels.
Put it this way.. 350z and etc are 21st century chassis, evo's except for the evo x, they're all 90's chassis. Evo 4 through to 9 got same chassis just different shell on top that goes back to early 90's.
Evo x probably got much better chassis. "
A few of my other friends had the opportunity to go for a drive with him, following in 350's, the "tin can", was very quick, and that's their words.
Hope that helps. He's been quite objective, but he calls a spade a spade.