We own a 2001 Eurovan and a 19' AS. The Eurovan is the Weekender model, not the full camper version. It does have the pop top.
I don't know which you have and what year. Obviously the best of both worlds would be to to the AS with the EV, but that is quite impossible due to the size of your trailer. We tow our 19' AS with the Euro, for now. And this is only in the mid part of the country where it is more ort less flat.
I wouldn't think of towing out west with our current set up.
Also, is it just one person (you) going on this adventure? It sounds like you'll be out for either one month or two. If you use the van, and asssuming it is either a Weekender or Camper, two should be comfortable, but there are many more things to consider, and set up at each stop.
My wife and I went on a one month driving trip from Chicago in our EV. The bigest hassle was setting up the bed each nite, and inflating mattresses. These also tend to spring leaks. We "lived" in our van for 30 nites. Not bad for two of us close to 50. We had a blast.
All of this trip was total boondocking, and we stayed in some of the most beautiful BLM campgrounds, most which we had to our selves. Showering was outside using a shower bag contraption that we always failed to leave in the sun to warm up. Cold water can sure do strange things to man-hood. Mercifully, only temporarly...
For sheer comfort, maybe the AS is right for you.
Let us know what you decide and if you have any ???.