Parking restrictions played a big roll in my decision. As I was planning to purchase my RV 6-8 months prior to my departure for Mexico, I wanted the RV at my home and not miles away in a storage lot. Parking at my residence allows easy access to power supply and tools. Local regulations on street parking for RVs limit the maximum length to 20'.
Fuel economy was my second consideration. With a budget of $600. per month, the difference between 6 mpg and 10 mpg is substantial. This difference has been further amplified with the recent skyrocketing of gas prices.
Mexican roads heavily influenced my decision. I follow several blogs about RV travel in Mexico. It is commonplace for bloggers to post about the limited access to small towns and villages; the circumnavigation of large cities due to traffic concerns; the difficulties faced when passing road construction sites and detours; and parking of large vehicles in general. Most blogs also post stories about going to town using buses, taxis or getting rides from friends in order to go into town. I want to go when I am ready and a shorter RV will facilitate this.