Hi Mate,
welcome!
Ive just sold my Zed and looked/test drove the VX220 around 2-3 weeks ago as a replacement. As much as i loved the VX it was for me too hardcore as an everyday drive. it did have its faults like you mentioned above which put me off but namely it was the build quality and getting in and out the damn thing. I'm no spring chicken but i aint overweight and i struggled getting out of the thing. Getting in was fine as you slip in the seat but as the doors don't have convienience hinges i had told hold the door with my head as i was getting out. Not good if i was in a car park spot. haha. The seats were like sitting on a piece of wood with cardboard wrapped round it, thats how i described how cushioned they where anyway.. Thats not to say they are all bad points as i liked the quikiness and how it looked in the flesh. I had to give it some serious thought on whether i'd get one or not but in the end i went for something else.
The 350z will be completely different, it will be like sitting in a limo compared to the VX, but you also feel its weight alot more when braking and cornering. The Zed's ride is much smoother than the VX's and doesn't crash over bumps like the VX does. I'd say the Zed is a slightly quicker car on anything other than a track due to its torque. I felt the VX engine was rather revvy and peaky and lacked alittle low down grunt. This could have been because i'd jumped from the Zed straight into the VX but i expected more from a 2.2 in a lightweight car...
What i will say is that they are both Great cars, but very different to drive. Everyone has different tastes but i think you'll enjoy the Zed. Although heavier its very balanced and great to drive. What i think you'll like more is the ownership experience. The servicing costs are pretty reasonable and you have the friendliest bunch of people on here to give advice, chat, laugh and help with any problems that you may have. It was one of the reasons i didnt want to get rid of my Zed...
Good luck anyway. The next thing to do would be to get an extended test drive... lol