Be concerned with the overall cost: initial purchase cost, taxes, depreciation, DMV registration, insurance, maintenance, upgrades/replacements, repairs, new tires every 4-5 years, RV park fees, and extra costs of living on the road, tourist attractions, restaurants, etc. MPG is only a part of the cost of owning and using an RV. Choose a length and floor plan that suits your needs and desires carefully . IMHO, a rear bedroom with "rv queen" bed access on both sides is a necessity, access on one side makes getting in and out and making bed difficult. Ample cargo and cabinet space is also important.