Having driven both standard (my brother had a e46 m3 convertible in carbon black with the smg gearbox when I had my zed), I'd say the zed was a thousand times nicer but then I might be a bit biased. Alright dude long time no see.
Having used tein springs at high speed, I'd say save up and go for coil overs if performance is your thing. At high speed mine didn't feel planted. Too much play.
Shell v power is priced at 7p per litre more than normal unleaded. Using my fuel calc and the figures from my zeds usage over that time it's worked out that 10000 miles would need 2268litres of fuel. I did some spirited driving and some motorway. So a good average. Ranges from 14 mpg to 31 mpg.
Therefore 2268litres of fuel would cost £160 more. It's not really a bank breaker esp when you consider you're driving a 30k sports car.
The roi zeds state that 95 is fine. By it's this because they've been mapped differently? Same with the US ones.
All I know is that when I decide to buy another zed, it will be one that's only been run on 98ron.