Comfort and convenience
Besides construction, consider comfort and living space. Vans and truck campers have limited space. If you are a solo traveler, you may do fine. Doing the do-si-do in a narrow aisle with a partner for months can get old. Consider also how comfortable the bed and the sofa is. Do you even have a sofa or comfortable chair? George and I traveled in a Lance camper on our Ford 350. It had a small slideout, which certainly increased the room. However, the only place to sit was the dinette. We could put our computers on the table, though the table was higher than comfortable for typing. We also read there. The only other option was lying down on the bed or to sit outside. The Lance was great for short trips but by the end of several months, we knew we needed a larger rig for travel and working on the road.
Smaller rigs like vans and campers have smaller refrigerators. It means more frequent trips to the store. If you are working or volunteering in a remote spot and don’t have access to another refrigerator, it will severely limit your supply of fresh fruits and vegetables.