In reality this is very much down to personal choice. There are clear benefints and disadvantages to both.
I think that if you plan to be constantly on the move a campervan would be the better choice but you will have to understand the benefits and restrictions. Some of these are listed below, i'm sure there are a lot more reasons but it is really personal choice. Many who tour with campervans would not consider a caravan because of the restrictions towing brings and visa versa many caravanners would not consider a campervan....but at the end of the day,
"We all sit in the same camp!"
Some campervan benefits: cheaper ferries, tolls and when touring it is much simpler to set up and leave site, although the big motor homes can be difficult to get on and off a lot of continental sites.
Some Campervan disadvantages: Once on site, no transport (unless you have cycles or a motorcycle) If you do need to go off site you need to pack everything away and I would think that would be annoying if only going off site for the day.
I also never see the advantage of towing a car with a campervan, if anyone wanted to tow then a car/caravan combination would win hands down!
The intiial outlay for a mid range camper can be in the mid