Trade-offs all the way around just be aware that to my knowledge major rental chains like Cruise America only offer gassers. If you plan on pulling any grades, a diesel is better especially with a lot of weight. We rented a 19 foot class c gasser from CA for a trip to Yellowstone. Two people, two dogs and it was a snail in the hills. You can buy a used diesel but you never know what problems you are inheriting.
So, if speed is not a problem and you don't mind crawling up grades, I would probably opt for renting from a nation-wide chain, you will have the support to cover any issues in case you need it.