I am looking to buy a 2 berth caravan around 10 years old, (21ft) I have never had a caravan before. I am aware that manufacturers bring out different improvements. I wondered with caravans if it is a bit like with cars in the 1970's when they introduced Power Steering which became the accessory to have when buying a second hand car. Obviously I am aware of Motor Movers, but what do I look for in construction improvements, heating, electrical sockets, I have looked at a couple of Swift Caravans, is there a better make. ? What would you buy at around that age. (towing weight is not important)
Only you can decide what is important or not to you, Motor movers are still an after market accessory and I'm not sure if any caravan manufacturer offers one as a factory fit option. so that in context of your question is a poor example.
But there have been numerous developments over the years often starting as an aftermarket modifications, or something that's quite niche which later became almost a standard feature. Things like solid walls
Adding insulation,
pumped water (initially they were manual foot pumps)
Space heating
Electric lighting
Double glazed windows
Fridges
Mains hook ups
Ovens
Water heating
Showers
Built in radio's
Television points and aerials
MIcrowaves (still a bit of niche market)
etc etc etc
The latest and in my opinion important change started about 10 years ago and that was the change to the wall construction away from wood and other compostable materials to more engineered solutions. It's only taken the industry nearly 100 years to decide that customers were right to be very disappointed with the the way caravans traditionally aged and rotted.
I do welcome such changes which do seem to have reduced some of the damp issues, but sadly there are still far too many instances where caravan reliability and quality are still very poor.
Most of the manufacturers can point to some examples of models where the faults that do occur are small or minor, but the very next caravan on the production line might be a very differnt storey and one that causes the customer no end of issues. They can build good caravans it just that they can't seem to do it consistently. And from what I have seen none of the major UK brands are significantly better than the rest, and even some of the continental brands can have similar experiences.
By all means seek opinions from forums, but becasue of teh manufacturers inconsistencies, do not assume your own experience will be the same as any one else's.
Of course teh other point about secondhand caravans is you are unlikely to know how it has been treated by its previous owners, so that introduces a lot of additional uncertainties.
I certainly advocate two key things. If you can take a friend who is a caraanner along with you when looking at caravans, their experience may help you spot some problems you might not appreciate.
And also as has been suggested above, especially with S/H caravans its a very sensible to employ an independent caravan exert to inspect teh caravan before you agree to buy it. Its money usually well spent.
Good luck