Interesting that the '04 is talked of as better than the '03. I have no doubt of it. As is the '05, '06' and '07
I suppose in a general development of a car the first years is where the consumer does the real road testing and development of it. It's a new design so they can sell anything without throwing in extras. Paint colours are more limited. everything is an extra.
By the second year the issues are known and developed out. Years 2 & 3 see improvements and we start to see the addition of extras that were previously chargeable. As we run out the 'MkI' we see adition like clear headlights.
Year 3 or 4 the sizzle has gone, the press is ignoring it and there are new kids on the block so it's facelift time. Usually a sham where external components are added that make the old one look slightly dated but not alienate the existing owner. So in the Z we see a new nose cone, new tailights, etc.
From here on in the car is sorted and it's 'cash cow' time. Keep 'em churning out and just start adding in extras that were previously chargeable. Add new paint colours, different wheels and perhaps even limited editions. Just run it out and keep it going.
Along comes the new model and we start again. Launch it with the least possible. Hell we can shift this sucker with fabric seats, amber indicators and plain paint........all we do is tell the public it's bigger, more economical has a 20% more rigid shell and a higher NCAP rating and off we go.
Not happened to the Z yet but 3 generations and the original model has grown so fat and lazy that a new smaller car one is slotted in claiming all the features of the original. Just look at the Golf from MKI to MKV now I think we have sporty small models slotted in claiming the spirit of the old Golf
So in this timeline any later car will be better, more equipment, improvemd components where needed and naturally have lower mileage, less wear and tear and of course cost more.
Cynical, but probbably not too far from true....
(Please please not a thousand examples of a later car having a specific major improvement like the 4x4 system on the X5 at facelift time. It's a cynical generalisation of the car industry)
BTW - I love my '03 but an '08 would be better