Hi Brian,
We are just changing to a caravan from a motorhome, after 20 years of those, the last 12 wintering mainly in Spain. The reason is really because we don't want two vehicles now we don't have far to travel and our Motorhome was UK registered so had to go, as we are now resident in France.
For travelling, a motorhome is great to drive. In Spain a caravan is restricted to 80 kph on motorways which is a drag.
If you are touring I think the motorhome would be best, but if staying on one site, the caravan would give you use of the car.
It is very risky to leave a motorhome parked in Spain off site, so someone really needs to stay with it if you go shopping or whatever.
I reckon that the proportion on Spanish sites in the winter is about half and half, so a lot depends on what you do with it the rest of the year. Quite a few motorhomes tow cars, but legally this is a grey area and cars on trailers are becoming more popular now.
James