Why a pop up? How about a normal campervan? There's loads of them about.
Is a question each of us must answer in our own circumstances, and there are many factors which will play heavier for some and others lighter.
The very basic choices are between :
- one vehicle only or two?
- if two vehicles, factor in the cost of running two vehicles (no no claims bonus on second, for instance)
- if one vehicle only, one big thirsty one, a bit harder to navigate and park in country towns, or one smaller one which is nippy about lanes and towns, and tows? (and isn't so thirsty when not towing)
- convenience of small nippy vehicle to go to the shops or out exploring once you are settled in your base vs having to strike camp every time you realise you need something else from the shop
- ease of striking camp : it does only take me about 20 minutes (if that) each end in the Eriba (without awning) but it would be quicker with a campervan
- forays and parkups when en route from camp to camp : slightly easier in campervan
- "wild camping" less obvious in campervan
- cost of purchase : campervans many times the price of a sturdy caravan
- cost of running : vehicle maintenance dwarfs caravan maintenance; depreciation massively more on campervan than some caravans
In my case, I did not want to run two vehicles and I like to run a very fuel efficient car, so that was a huge factor for me. (It's nearly as thirsty as a campervan when towing, but it drinks a lot less all the rest of the time.) Also, I did not want an outfit that was unreliable, and a campervan that was new enough to be as reliable as my little runabout would have cost 5-6 times as much as the caravan I bought.
Things I had not factored in included that it's not so easy to pick up provisions en route with a caravan behind - although I do usually manage to find two slots facing in a supermarket car park, or a double length space on a roadside. And that I felt nervous about leaving the car and caravan parked up out in the wilds if I wanted to do a walk en route to or from my destination, although I am getting less anxious about that these days. Wear on the car tyres mean I replace my car tyres very much more frequently now, and buy better quality ones. One that sounds silly, but really affects my choice of travel route and times : the parking at motorway services for caravans is always a gazillion miles from the actual services, and if you have a dog with you, in hot weather that means either bringing the dog to the services with you and risking leaving it tied up outside, or half setting up the caravan and putting the dog in there while you go to use the facilities. Or, carrying plenty of water, forgoing the Costa coffee, and, ahem, making ones own arrangements for ablutions. (Not a problem if your caravan has a bathroom; mine has a bucket

)
I have friends with caravans and friends with campervans, and each can see things about the other choice which would be nice. For me, I would like the additional freedom of just deciding to stop here overnight; there are many, many more places you can (in practical terms) do that with a campervan than a caravan. And similarly, deciding to fit in an extra walk on the last day. It can be done with the caravan but it requires a bit more planning, knowledge of the roads - and more luck with parking. But friends with a campervan envy me being able to set up camp and then pop to the shops in the car, and being able to leave the 'van set up while I go out exploring for the day, come back and fall straight into bed. And having the nimble little runabout (which is pretty cheap to run) to use both when away and around locally when I am at home.
It's always going to be a tradeoff, I think, and each of the factors will weigh differently for each individual - and may change as one's circumstances change, too.