Boy, are David's experiences with his Canyon similar to mine with my Dakota? The 3.7 in the Dakota is rated to tow nearly half again what David's Canyon was, but it sounds like it performed about the same. Pulling hills at 4000 rpm is tedious and it REALLY sucks the gas. I, too, would have gone back to a full size tow rig, but many other personal circumstances made me settle for my 4.0 Tacoma Prerunner. The Tacoma and, I've heard, the compact Nissan pickup, do well with towing RPods.
Brewsterivy, I don't have any experience with Casitas, but have done some campground discussions with Casita owners. They report better mileage and easier towing due to the Casitas' less wind drag, as they push less wind from hiding better behind their tow rigs. Casitas do give up some in the areas of elbow room and sleeping space. They are, I've heard and seen, nice trailers.
RVing is so much fun and sometimes so frustrating. What fits perfectly for some is a major pain for others.